Mages – their development.

I only level up the counterspell if I manage to level up empathy as well. My favorite mage is Orah. Even without empathy, she casts spells more often than any other wizard. Moreover, I also level up wizardry for her.

The most annoying thing is when a counterspell is dispelled not by the hero with a cheap arrow, but by some spellcasting unit. If the enemy uses a counterspell, I dispel it either with a unit or with the most expensive spell.