[Taqwus]

Formations get ugly.

The AI does not deal all that well with damage-aura effects on two levels:

(1) initial unit placement and selection, and
(2) dealing with them on the battlefield

ex. (1), I've seen a Sauromatian army with hydras placed in the center front, with other living non-immune troops. When they fought my Ghost Riders, there was massive own-goaling through poison because it took them a while to kill the wraith lord.

ex. (2), I'm inclined to think that a non-mindless, non-immortal unit should be reluctant (morale check?) to run or stay in a damage cloud to which it is not immune. If it's not in the cloud, it may make more sense to either go around, or hold.