I haven't gone through 16 pages of posts, so forgive me if this has already been addressed.
While Chimera is a good card under certain conditions (mostly as a finisher to bypass shields) I have noticed that the AI is *really* bad with it. For instance, I was just facing off against the FG Akebono, and was stalling a losing battle against a horde of overdriven Massive Dragons. I kept dropping sundials to stall, and with my last sundial about to go, the AI played Chimera, and turned his entire army into a giant behemoth with triple digit attack/defense. The sundial made him pass without attacking. I then immediately used the Fallen Elf I'd played the previous turn to turn the chimera into an abomination and ate it with my Elite Otyugh. Yum!
I've seen similar situations in which the AI scooped its entire army to Chimera when a clear way to kill it was on the field. (Eternity, Fallen Elf, etc)