Honestly I think this is great. A very elegantly simple mixture to create a new addition to the Trolls WHICH, importantly, doesn't have a mohawk or crazy-bowed-legs! I mean I love those things, but you see them on ALMOST LITERALLY every single Troll model & it gets passé.
This gives a Jungle Troll race a unit with a unique form/animation profile (at least compared to existing standard in-game stuff; cinematic stuff doesn't count so it's good for that), and since it's made from in-game parts it fits perfectly. Even better, you have the model, it's Portrait, and an Icon!
If I might suggest a few changes that could really enhance this (or at least help differentiate it, especially in-game next to the existing Warlock), consider rewrapping the textures (especially the ones for his clothes). A new UVWrap, perhaps with more Trollish materials (cloth, leather, wood, bones, etc) could give this model a real facelift.
Possibly also (minor), change the color of the particle SFX in Spell/Stand Channel as well.
Good luck.