As per request of EternalRage here is my 300+ wave fireball build.
You are using meteor every 4 seconds to keep up Craterborn and we scale a lot of crit+crit multi for big fire burst damage. This build has both excellent single target dps and good aoe clear.
We are abusing 30% less elemental damage taken from Prism Wraps due to capped elemental resistances, orians eye and high amount of leech combined with flame ward makes the build extremely safe
Idols are straight forward the only thing that matter is the suffix increased fire damage.
The black sun - Critical multiplier
Ending The Storm - Chill chance
Dragon’s Reign - Crit avoidance