I feel the bear is already fine in itself, in that he offers vaiable ways to be played (e.g. pure phyiscal, fast-dashing, stay longer in shifted, physical caster, mage caster, pure caster, hybric melee/cast). And he can be quite fast and insisting, therefor I wouldnt really need another form such as an agility-raptor or something.
I find Poison to be an ailment he could go with, adding lots of variety. Not a particular form either, but something that is akin to nature:
“Formless form”. It`s like the breeze of the wind, or condensed water, becoming the very Atom of nature - turning water to Poison to ail his enemies. Shifting Elements on the fly.
Cloud of the vaporised -first ability, “W” button
Become formless for up to 3 seconds, spreading more widely across the floor each second passing on poison onto enemies afflicted (e.g. 2 stacks per second). This means, you press the button, then you vaporise onto a poison-cloud that drifts further away from the Ground in all directions (spreading AoE - you cant move during the Duration), poisoning enemies affected each second. After the 3 seconds are over, or when you activate the skill again during its Duration, the Cloud forms back to form (the “formless” form, of Course) at your Cursor (and may do something else then, e.g. poison one enemy hit on Impact more intensely). You probably take much reduced damage during the process, or no damage at all (in which case you also do not Regenerate health).
Spread Invisibility - Right Click button
You spread the formless onto foes, which cracks their very Atoms - poisons x times per second for x seconds, spreading among foes (stackable). This could either be melee, or short-range casted ideally. Few metres from the enemy, so you are close and Always on the go (a Fitting theme within the skills he uses)
Release Tension - “E” Button
Whenever you move or attack or being attacked, you stack “Tension” due to having to hold your formless state, which then Needs to be released. The Tension goes up to 100, and can be released at any time and will grief out to 3 enemys when released (perss “E” button), dealing direct (poison) damage to them. Not a DoT. More Tension = more dmg.
This is an “active passive” ability akin to the one mage is going to get.
Form a Sect - “R” button
You summon insects that follow you and attack enemies with poison-ailment (they will be akin to the small helpers the scorpion can summon, following you around on the floor and being small and nasty) - 3 second CD, 3 summoned insects total.
When all are active, activate this ability for each insect to increase poison-ailment-application 3-fold for 1,5 seconds, so each attack applies 3 stacks of poison instead of 1 (7 second cooldown).
Formless nature-boy! The tree´s could possibly swap stuff in regards to damage type, obviously: physical (wind) and ice/Lightning (storm).
So the insects could be wrath-bees of Lightning, or small stun-tards of physical.
The “W” ability of formless form could roll a thunder-cloud doing Lightning damage or chilling in a frost-mist dealing Cold. etc.
The “Right click” button could do lightnings with increased range - or even Shorter range spawn but higher Impact! Melee-caster) etc.