Sorry for the delay in the PEACH, but here we go.

You're going to be berserking a lot, especially because the highest Concentration check a player can make is proportional to level, but the DC is proportional to rounds times (damage-INT mod, a tertiary stat). The check might be failed on the first round, but it will probably fail on the second and will definitely be failed on the third round. I like the mechanic, but I strongly suggest aggressively increasing the berserk Pool's recovery. I suggest it divide by a constant at the end of each round, probably two but maybe three. Also, wouldn't it make sense for becoming calm to base itself off Wisdom instead of Intelligence? (For example, see Bruce Banner)

Chimera's Armor does not specify a "flat amount".

Chimera's Claws does not specify what the damage dice of the claws is. It does in the table, but not in the text. I'd add it to the text anyway.

Aspect of the Beast is cool, but I can see it leading to lots of combos. You might want to consider instead taking evolutions from Pathfinder's Summoner. They are "a wide variety of modifications and upgrades that add new abilities, attacks, and powers" like a tentacle, a breath weapon, wings, an extra limb, and so on.

Overall, I think the class is really cool. I don't know how I feel about having loss of control built into the main class feature, but I like the premise and it seems well-executed. If you're looking for more things to give it, I'd suggest different class features that emphasize it being a natural disaster. Great Cleave as a class feature, fast movement, and so forth.