[Nerfix]

It also helps to check what type of damage the spell does. Type as in whether it is normal, armor piercing (good) or armor negating (priceless). Bladewind does normal damage and thus can be blocked by armor. Fire spells do armor piercing damage (generaly speaking) and are more effective against armor, but armor still effects the damage it does. Some spells like Astral Fires and Mind Burn do armor negating damage that ignores armor.

Checking if the spell can be resisted by magic resistance is also useful. Don't try to use Astral Fire, Mind Burn or other Mr-resistable spells against high-MR units.

Having the mage cast path and/or precision boosters can be VERY beneficial. Especially Summon Earthpower, which gives reinvigoration. Aim and Eagle Eyes can make the mages substantially more accurate with spells.

To put it shortly, know what tools you have been given and how to use them best.