autoresolve doesn't work amazingly in general, i feel. The unit with the lowest defense seems to almost always take damage, even if it's an archer and you\re facing a horde of slow moving melee creatures.
restricting mana usage would be nice, yes ^^
Oddly my experience is that it is usually the *last* unit in line that takes 99% of the damage. This is left to right, top to bottom. Meaning, I always put a golem in the last slot and they take all the damage for me, unless it is so bad that it kills them and they it seems to work in reverse order anyway. 2 golems is even better.
Reloading a game changes the order again, as the save does not preserve it. So sometimes I have to move the unit I want at the back out of the stack and then back it.
I'm sure it is some sort of bug that should be fixed.