What class is your creature? A mage head would probably be better than a ranger head, and either better than a warrior head. A demon summon could also help, if you have a skill point or two to spare.
If you stick close to Zandalor you should have an easier time protecting him. I stayed in front of him to cover those two rifts, occasionally having to Rush Attack a memory eater from the rift in the back. A bow didn't do a great deal of damage (didn't invest in any ranger skills), but it did help draw opponents to me, rather than have them go directly to Zandalor.
I was level 35 or 36 when I did that section, one of the final things before heading to the hall of echoes (duel wielding maxed, level 10 Bleed, etc).
If you are not already playing on easy you could temporarily lower the difficulty.
If you completed Keara's fortress fairly recently, and have a save before solving the statue puzzle, you could keep clicking on the door there to spawn more opponents, in order to level (
how to reach level 40+).