I have tried before Summon Vermin and summon Skeleton, but I didn't find it satifying ...
I agree, on Hard, summons really have a tough time. Poor scorpions get slaughtered very fast too (I'm playing the download version where they have been nerfed).
I had two mages killed at ~lvl 15, twice they got one-shotted by Giant Heavy Orcs
But up to there they had been really easy, ranged attacks are the way to go in the beginning, and harvesting corpses/zombies and orcs for XP and items. I just don't feel like starting over another mage, I think I'm going with a Warrior and maces/ body+spirit magic or a spear-thrower.
Keep it up!