My spellweaving mage has outperformed every one of my other characters in Magincia, including my archer.
The secret is not getting killed. With a mid-to-high focus and the renewal spell, I find I can run into the thickest of the spawns, drop two energy vortexes, then run back out.
Looting, however, has been a problem. I solved it by looting other people's kills, since by the time I can get at them, the person who mad the kill obviously doesn't want it. My vortexes in the middle of the spawns have gained me many cursed arties and even one staff of pyros.
At the bone-and-light spawns, I cast nature's fury (for the light, I'm sure blade spirits would work as well) or energy vortex and spend the rest of my mana healing the warriors who are pounding the things. It gets me kill-credit as well as the thanks of the people I help.
The only thing I avoid at this point is the dark fathers, unless there's a lot of other people around. It seems that alone, I can't even dent the things.
The one thing I have that most people don't is that my protection is always up. You don't need high fast casting for healing and energy vortexing.