Well, not Arco (didn't need to
) but I did try my hardest with Pythium and Man (only he disappeared just then). Only Azhur knows what it amounted to, though...
If there aren't any enemies within 7 squares of the caster, the tac AI won't use immolation - and a good thing too, since it's a one-time effect, unlike fire shield. So it's more like an even shorter range flame eruption. (Thus the proposed script to get the caster mixed with the enemy!)
True, you don't have much of a choice far as the attack goes... It's surprisingly effective, your army. Hell, it's better than CUnknown's Bane Lord -filled armies for this purpose, blitzing to my castle and storming it. I don't even know if my counter-plan will work! This is interesting, indeed!