Have as many group members as possible fight ranged to avoid the curse, which will lower any recipient by about 4 levels. I'm not sure exactly what the distance is, but if you stay ranged, you will not have to worry about it. Having 2 healers is really helpful so MT stays cured. Any other melee should fight through the curse, and leave the cures to the MT.
Fight through or cure any other detrimentals, they're not really an issue.
Pull him into a corner to avoid his knockbacks, which seem to be frontal.