This is actually a straightforward fight from an enchanters point of view. As you fight through the castle to reach Grummus there will be various adds most of which can be mezzed. All adds were no more than level 62. Go into this raid with you standard spell line up and just be aware of what can and cannot be mezzed:
Mobs which can be mezzed:
a firebone caster
a pestilence priest
Mobs which cannot be mezzed:
Guardian of Pestilence
Guardian of the Crypt (some appear innately immune, others not??)