[shatner]

For what it's worth, 100 precision spells (many of which are astral in nature) hit just fine even in darkness. Also, Solar Brilliance (also astral) cancels out darkness, though you'll probably want to cast antimagic first to prevent your troops from being blinded. Quest for the Firebird (or something like that) summons a unique creature which casts Solar Brilliance automatically at the start of battle.

Beyond that, undead and demons can all fight perfectly in darkness. But yeah, darkness is a major barrier for everyone else.