I've not seen the passive AI bug at all since the patch. On the other hand there is a very obvious "cue" point in any battle - the moment any troops engage in melee combat, the computer opponent decides to attack with as many melee troops as possible.

It looks to me something like:

IF (I have lots of melee) AND (player has lots of missile) THEN ATTACK WITH MELEE
IF (I have lots of missile) AND (player does not initiate melee combat) THEN ATTACK WITH MISSILE
IF (I have lots of missile) AND (player initiates melee combat) THEN ATTACK WITH MELEE