You could certainly use a few more levels. I tried that quest once in the late twenties, or so, and had trouble killing creatures fast enough, but didn't have any problem in the mid thirties (left this until one of the last things before heading to the Hall of Echoes).
I stood a bit in front of Zandalor, with my creature summoned, and used a bow on opponents from the front two rifts (more to draw them towards me than to do damage, since I was playing a warrior with no archery skills), and occasionally had to Rush Attack a memory eater from the back rift.
