This is my take on the Firebrand/Flame Reave interaction with the new Spellblade passive tree. You can get around 1-2k ward on bosses & easily tank through all of Abomination, Void Rahyeh & most of Formosus’ attacks.
Updates
16/10 - 0.7.10c removed the effect of Charring’s bonus from Flame Reave 
a minor nerf but not entirely surprising
15/10 - updated @Krypt’s strict/BIS loot filter
14/10 - Added @Krypt’s loot filter & stricter loot filter
11/10 - Empowered Abomination video
11/10 - Lagon video + blessings
10/10 - Emperor of Dragons video
10/10 - Harton video
09/10 - Updated the gear section
08/10 - Formosus video, very bad gear…
How it works
Firebrand is a new skill & it has some interesting interactions.
When you attack with Firebrand it gains 1 stack (2 with Conflagrate node) of Firebrand which adds flat melee fire damage (can be converted to Lightning) & makes Firebrand larger. The main interesting nodes are:
- Incineration, using a non-Firebrand skill consumes the stacks of Firebrand for 20% more damage per stack consumed.
- Illuminating Fire, consuming 3 or more stacks of Firebrand gives the consuming skill a guaranteed crit
- Wildfire, more stacks!
- Pyroshielding, ward per stack if you hit something
- Fading Flame, ward per stack consumed (or expired) since we’re regularly consuming stacks we generate quite a bit of ward
- Conflagrate gives you an additional stack of Firebrand per hit. Not necessary, but certainly nice to have.
So, you hit 3 times with Firebrand to get your max 6 stacks (this will also have generated 243 ward), you then use Flame Reave to consume those 6 stacks for +120% more damage on Flame Reave & it automatically crits, plus consuming the 6 stacks gives you 363 ward plus however much ward you get from Flame Reave.
Skills
Firebrand
The workhorse of the build & what empowers Flame Reave to do 20k + crits on bosses.
I mentioned the most important nodes above, which will take 14 points. IMO, the other 6 should be spent in Fulmination (attack speed per stack) & either Pyroshield for more ward when you use Firebrand or Undying Fire for longer duration stacks (more time to manoeuvre into a better position to use Flame Reave).
I didn’t really like Triple Strike (3 lines of Firebrand per attack, +10 mana) since it can’t shotgun & the angle “off centre” the other lines are isn’t particularly big so it didn’t really seem to useful for me.
If you want to to a Lightning version, you’d definitely want to take Galvanize.
Flame Reave
The big damage skill that nukes bosses & trash. There’s a very nice new node on it that boosts it’s damage, size & range (though the size doesn’t appear to be working) every 4th Flame Reave. The node after it allows Firebrand/Mana Strike uses to fill in for those 3 normal sized Flame Reaves, which is very convenient since we need to use Firebrand 3 times to get it to full power!
Important nodes -
- Rhythm of Fire, every 4th use of Flame Reave gets +100% width (doesn’t seem to work), range & damage
- Versatility, using Firebrand or Mana Strike counts for the 3 uses for Rhythm of Fire
- Scorching Tide, more damage against ignited mobs!
- Ashen Waste, more crit multi for a skill that always crits!
Mana Strike
Unfortunately all of those Firebrand/Flame Reaves are pretty expensive so you’ll need to weave in 1-3 Mana Strikes to get back to full mana.
This I just spec’d for the most mana on hit I could get plus more AoE & out of mana hit damage.
Enchant Weapon
This can provide a very big damage spike for ~9s out of every 15s with it’s flat added damage & % melee damage.
Molten Steel (added flat melee fire damage & % melee fire damage), Concentration (duration), Efficacy (lower mana cost & increased melee elemental damage) are the most important nodes. When you have them maxxed out it will provide a very big damage increase, which will be buffed by the x2.55 crit multiplier.
Teleport
You don’t need to have Teleport specialised, but the decoys are nice.
Passives
I’m only lvl 72 at the moment, so have a ways to go, but here’s what I’ve got so far
Mage:
- Scholar, health & mana
- Arcanist, Int & Fire/Lightning resist though you could also go for Elementalist if you wish for more damage
- Mage Flurry for more attack speed
- Knowledge of Destruction, for more crit multi, currently only 5 points but I’ll max this later
Honourable mentions:
- Warden for more ward retention to keep that ward for longer
Spellblade:
- Elemental Affinity, damage & resist!
- Infused Weapon, flat added damage (only fire for us, but if you went with using Mana Strike as the main damage dealer, you’d get Lightning damage from it)
- Arcane Warden, up to 40 ward on hit! In addition to the ward you get from Firebrand
- Arcane Shielding, % damage reduction & ward per second is always awesome
- Warden’s Echo, 1 point to unlock
- Defender of Welryn, ward retention, will probably max later
- Shattered Aegis, gives you up to 80% armour at the cost of lower effectiveness on Arcane Shielding but overall you’re ahead
- Essence Duel, more ward per hit plus attack speed
- Mana Reaver, this is difficult to know when it’s working, but it’s added health & up to 30% chance to regain 10 mana when you hit at least 1 mob
- Prismatic Blade, more flat damage
- Volka’s Razor, 15% increased damage for Firebrand & Flame Reave! Per point!
- Mental Fortitude, added Int & some ward per sec
- Prodigy, ward per sec per 10 int
- Blade Weaver, 3 points for 45% more damage, but you’ll need an amulet with a t5 mana efficiency affix to get the cost of Firebrand below 10
Sorcerer:
I’ve not taken anything in this tree, but Mana Shell (mana & armour), Wisdom (int & mana) and possibly Pyromancer/Lavamancer (for the fire pen) look interesting
What I didn’t take:
- Elemental Strikes, we already ignite everything we hit, so no need for more ignite chance, though you could go with this until you get Eye of Reen
- Flame Walker & related nodes, I wasn’t really interested in Fire Auras, but you could if you wanted to
- Frozen Steel, we don’t do cold damage, we’re fire, plus we don’t use a skill with an inherent chance to freeze so the freeze multi would be wasted
- Fire Blood/Storm Blade, flat damage, these could be useful but we can get more flat damage from Infused Weapon
- Inferno/Flame Drinker/Blades of Fire, if you go into the fire aura nodes, you’d probably want to take these to buff them but we aren’t so…
Gear
About the only "important piece I had was Eye of Reen. Every melee crit (& Flame Reave always crits) gives you a stack of Reen’s Ire, which grants 5% crit multi & 5% fire damage over time (not particularly important, but we do ignite lots). In the first quest echo for Fall of the Outcast, I was able to get ~120 stacks of Reen’s Ire taking my crit multi up to 2.15 + 0.4 + 6 = 8.55 times my normal hits. But that’s a very rare occurance as it requires you to hit 120 mobs with Flame Reave which requires you to pull that many mobs without dieing in the first place…
Additionally, I used Woven Flesh for the leech & 100% crit avoidance.
Other gear needs to be used to cap your resists & get as much health, int as possible. I also used a shield to benefit from the ~50-60% damage reduction on blocked hits (40% block chance at the moment).
You should also get as much chance to apply frailty as you can, as this provides up to 18% damage reduction, you can get it as a prefix on ring, relic & gloves, t5 affixes will give you 28%-35% chance to apply Frailty, you want 2 of them.
This is what I’d like to get for gear in terms of bases & affixes.
As far as useful affixes by gear slot:
Helm
IMO, the Silver Crown is probably the best base, since it gives us ward retention, with honourable mentions for Celestial Helm (more armour & mana), Solar Crown (fire damage),
Prefixes:
Set Necrotic/Poison & Set Physical/Void resist are probably the best to go with here unless you’re getting the required resists elsewhere, then either Set Elemental resists, Int, Armour or Dex (damage) and Vit (more hp).
Suffixes:
I’m not too interested in the Mage-specific affixes, though the Fire Aura on kill with Fire skill might be interesting (then you may wish to go down the Flame Walker passive nodes route), and we don’t need Crit Avoidance so I went with Ele resist and Armour, though you could go with any of the other suffixes if you wish, such as Fire DoT, Health, Mana & Ward per sec.
Amulet
Oracle amulet is probably the preferred defensive base, but Jade would be good for offense (more attack speed) or Ruby (health).
Prefixes:
Since this is where some interesting affixes are, I chose to go with
Crit Multi (Flame Reave always crits)
Fire Pen (we do only fire damage)
Other good affixes would be Fire damage, Elemental damage (less so that Fire damage as the numbers are smaller), DoT & Ele DoT if you wanted to buff your Ignite damage.
Suffixes:
Again I went for Ele res & Health here, honourable mentions are Armour, mana & any resists you’re missing.
Weapon
Eye of Reen is probably the best here, since the Reen’s Ire buff gives crit multi & Fire DoT damage. I tried Alluvion & it did a bit more hit damage which was a bit surprising since it’s base damage is much higher. An alternative might be a crafted 2-h weapon (probably a sword) with melee phys & either attack speed or melee fire damage as prefixes & stun chance with melee attacks & either Frailty, stun chance or possibly all attributes (mainly for the Int & Dex for damage & ward retention plus a small buff to armour from the Str).
Off-hand
If you’re going for Eye of Reen, then either a Kite Shield (lower block chance but higher block effectiveness) or Solarum Shield (higher block chance & lower block effectiveness) is your best idea.
Prefixes:
Block chance (obviously)
Then either block effectiveness (more damage mitigation when you block), armour (more damage reduction on all hits regardless of whether you block or not) or health on block
Suffixes:
Damage taken on block
Ele/All resists
If you’re ok on resists, armour or health are goog choices
Chest
Woven Flesh, 100% crit avoidance frees up a lot of affix slots & you get decent armour, health, leech, OVERKILL LEECH (you’ll be doing stupid amounts of overkill on trash, so suck them all up 
) & faster leech!
If, for some reason you don’t have a Woven Flesh, then Archmage Robes (mana spent gained as ward) is probably best, or Battlemage Robes (ward retention) is also a good base. But you’ll need to get that crit avoidance from somewhere else.
Prefixes:
Int
Armour
Not really much else that can go here. Our skills cost too much to concider damage taken from mana before hp IMO
Suffixes:
Mana spent gained as ward
Mele elemental damage
Belt
Bronze belt (lots of armour & 4 potion slots)
Prefixes:
Set Necrotic/Poison resists
Set Phys/Void
The belt prefix slot is lacking in awesome affixes, unless you want to go potion effects.
Suffixes:
Hybrid health
Armour
If you’ve not chosen to go with a Woven Flesh, grab some crit avoidance here
Rings
Personally I prefer the Gold ring (ele resists), but Ruby (health), Copper (stun chance, we do big hits which will naturally hae a higher stun chance) & Silver (movement speed) are good bases. Since we also crit so much, 1 Ring of the Third Eye might not be a bad idea, but beware it’s -30% crit multi reducing your damage.
Prefixes:
Frailty on hit, you need to get this somewhere, rings are as good as anywhere
Int
Honourable mentions for Fire damage/Ele damage, DoT/Ele Dot, and the set resists prefixes if you’re lacking those resists
Suffixes:
Armour
Whatever else you need to fill out your resists
Crit avoidance if you’re not going Woven Flesh
Gloves
I went with Engraved Gauntlets here, since we don’t need the crit chance from Solarum Bracers (though that would help with the non-Flame Reave hits, so it’s not a bad base if you get good mods on it).
Prefixes:
Attack Speed
Int
Or set resists if you need them
Suffixes:
Ele resists
Hybrid health (flat added health & % health)
If you’re not going Woven Flesh, you can get crit avoidance here, or anything else that you need to cap your resists
Boots
Arcane boots (low armour but ward retention), Solarum (high armour, fire resist), Heoborean (decent armour, cold resist) are all good bases.
Prefixes:
Set Necrotic/Poison resists
Set Phys/Void
Not much else that you might really want to put on here.
Suffixes:
Hybrid Health
Movement speed
Crit avoidance if you’re not using Woven Flesh (see why I went for it? It frees up so many slots!)
Relic
Either Stained Tome (health) or Radiant Crest (crit multi!!!) depending on whether you want offence or defence.
Prefixes:
Set Necrotic/Poison resists
Set Phys/Void
You can put quite a lot on here, so, Frailty, Crit Multi, Fire/Ele damage, Fire DoT/Ele DoT, Hybrid Leech are all good prefixes.
Suffixes:
Much more disappointing than the prefixes, I went with Armour/Health, but yo ucan also put on Ele resist, Mana & other resists.
Monolith modifiers
As @Grimtok suggested, the main modifiers I try to avoid are:
- Dodge (this is hideous & should be avoided like the plague)
- Crit avoidance / Glancing blow (annoying & will halve your damage, but not “too bad” IMO)
- All resists is the given % reduction to your damage, so I’d rather not take it but it shouldn’t be “too bad” either
- Enrage, as long as it’s not on for the final quest echo boss it’s ok since the normal monolith bosses die pretty quickly
- Chill/Slow are also annoying but not too bad, more annoying than Armour shred/Mark for Death but all 4 modifiers will fall off after a few seconds of not being hit
Blessings
While you don’t get much choice in the blessings, these are what I would choose if I did get the choice.
Rahyeh:
Crit multi (20-26% from the normal monolith or 27-40% from the empowered one)
Fire damage (30-50% from normal monolith or 51-80% from the empowered monolith)
Lagon:
Ele Resist (10-14% from normal, 15-20% from empowered)
Ward per sec (10-19 from normal, 20-30 from empowered)
Mana (30-50 from normal, 51-80 from empowered)
Dragon Emperor:
Block effectiveness (400-800)
All resist (8-15%)
Levelling
Since you don’t get Firebrand until late, I levelled as a caster with Lighting Blast, Ele nova & Focus. Originally the build was going to also include Static to proc Lightning Blast, but with the changes to shock (only gives lightning shred) & the mana cost, this was a bit of a no-go. Life became much easier when I got rid of Static/Lightning Blast & used Enchant Weapon and Teleport instead.
For skill points, I tended to put in points in the order I gave above until I unlocked the next level, then moved on to the next passive, coming back to max out nodes later.
Video
Empowered Abomination:
Empowered Rahyeh:
Formosus:
Harton:
Lagon:
Emperor of Dragons (for the first time):
I did try Alluvion, but it did slightly higher damage as an Eye of Reen with slower attacks & no shield (less tanky) on the dummy. Though it does also have the wave on melee attack.