220% weapon damage for less mana than most spells and more range than most spells, is there anything that beats that? I've been using Dire Bats almost the entire time since I've got them and just haven't found anything to replace it. Most spells do less damage per cast than Dire Bats (at least, based on the tooltip), so the only benefit is positioning (going over wallers and whatnot).
The only exceptions I've seen are Haunt, which takes 4.5 seconds of damage (1.5 seconds with Resentful Spirit) to be worth one Dire Bat cast, which is problematic when you can only have one per target, and Locust Swarm, which requires 4.8 seconds of uptime to be worth one one Dire Bats cast. So, Haunt may be better single target, but typically fails when there's more targets (all the time). Locust Swarm is occasionally better spread damage, but it's got worse range, and either eats through your mana too fast or sacrifices some of its potential damage for a mana regen (but, if you're not using Devouring Swarm + some other mana intensive spell, like Dire Bats, it's often wasted).
Almost everything in the decay section seems like it's almost outright inferior to Dire Bats.
Zombie Charger: often less damage, less range, more mana.
Spirit Barrage: Less or similar damage and SINGLE TARGET.
Acid Cloud: Typically less damage for more mana. Range is really nice, though.
There's Hex Chicken: Less damage for a radial AOE on a CD? Why?
So, is there much of a reason to use anything other than Dire Bat spam in most situations? I could see a use for Dire Bats + something with stronger single target, but everything else just seems to be made nigh obsolete in comparison to Dire Bats.