I didn't have much problem with the nests, though I was a couple levels higher. Does one shot of Fire Sphere kill memory eaters for you? The nest should not be able to spit out more than one every 5 seconds (IIRC that is the cooldown time for Fire Sphere).
I assume you keep moving as you are attacking? (hit target lock for nests and circle around while holding the Fire Breath trigger/key down)
Did you try the summon spell? I didn't use it, but someone else posted that it was helpful in drawing off the focus of many of your opponents.
Did you lower the difficulty setting, if you are not already playing in easy?
