I played in the Open Beta and due to the fact that the progression saved from the beta, I can't get the achievement Feed The Beast. I am level 22 with the Chimera and do not have the achievement for getting the Chimera to level 2.
I’m also experiencing this issue on Steam.
In the Open Beta, I surpassed Chimera level 16. I have since full release leveled up, but am now Chimera level 17 but still have not received the achievement.