I am running a clean, updated install on Windows 7 64 bit, patched to latest level. Started a new game. What I have noticed is that ranged special abilities of my summoned elementals tend to automatically miss if used at max range. For instance, my big earth elementals cant hit anything with their AOE, and the fire elementals always miss their fireballs. However, my heroes pretty much always hit. If I move up the fire elementals and use their fire breath attack that attack will hit, but the fireball doesn't. Have not tried that with the earth elementals since they tend to get dead if they move up too far. Have not made any archer units yet, that may be my next experiment. I've been playing on Tiny maps for quicker gameplay, don't have the stuttering others report that way. 

Spells - I should say my heroes throwing Fire based spells do well, lightning seems to be over-nerfed. If they hit at all it's for negligible damage.