My big complaint with mages was resists. Some dungeons/mobs were heavily resistant to my primary spec damage type, making them either unkillable or very tedious due to a lack of efficiency when using alternate spells. Spell hit was OK but when you have e.g. elementals that are immune to your damage type, it's a real PITA. And this is classic, so it's not like you can just go respec every dungeon without being a gold farmer's family member.