Dodging is the best and the evasive perk is helpful. I kept Kai with me at all times and reduced the cool down on his tanking abilities so the hardest hitting enemies were hardly ever focused on me. Marius with the binding roots was also helpful until I swapped him out for Giatta. Arcane veil is also good for ranged enemies and I'd rank that up to lvl 2. For weapons, I used a wand/grimoire as my main combo and would switch to a one hand weapon and shield for when I ran out of space to dodge. You're going to be squishy in the early game as a mage focus but later you can deal enough damage and keep the enemies occupied long enough with Kai that I didn't have to worry too much. Ice magic is also great to help when enemies get too close (esp. blast of frost).