Came from PEACH exchange:

Very interesting. I tried to make something similar once (a PrC based on wildshape), but failed at it . Anyway, this is pretty neat. It looks like heaven for a min-max-player though, not sure if thats good or bad. Its hard to judge how strong it really is, probably pretty strong due to its flexibility (Tier 2?).

Some pointers and suggestions:
• Maybe make it so that adopting multiple forms increases Beserk Pool DC somehow, seems to make sense and may balance this a bit more? You could make fewer forms a bit easier as you level in the class. This way the player requires to make some considerations between power and reliability, thus introducing a bit more depth to the class.

• Maybe introduce some sort of absorption/study/anatomy feature, where you actually have to encounter a form before you can adopt it. Sort of "gotta catch them all" idea. If so, add some tracking skills? Not sure, just a idea that seems to fit. It would also give the DM a more subtle control over the class. Such a feature could also lead to cool track-and-hunt side missions.

• I don't think dragons fit well in this list to be honest. I would rather see Monstrous Humanoids.