Well, my mage build was all about kiting - take a shot or two, run, take another shot, run, take a shot. Make sure a mana potion is bound to a key you can press easy and use it while running if needed. The tricky part is when you run out of room and have to try and slip by them to run the other way.
With the battle at the hunters' cabin, I had all sorts of allies. "Dork" the ogre, the two hunters, and their pet wolf. I just stood back and tossed fireballs into the crowd. (The fact that the good looking gal's husband and pet dog both died in the battle was TOTALLY not my fault, I swear!)
You spend a ton of time in the volcano so I can't say what the deal is there for sure, but I bet it's that little lizard man village. I defeated that by using conjured skeletons. After clearing the top near the little hut (which was done with the normal kiting and a little help from that poor miner), I dropped a skeleton just to the right of the hut and down a bit so the skeleton could block the oncoming horde. That let me drop fireballs into the crowd while they delt with the skeleton. Once they broke through, I would try to pick off whoever was hurt most then run, get my health/mana back, and do it again.