The adds on this are mezzable so feel free to do that, then rush the terror. We did end up taking out the adds because the mezz broke right around the time that the DDA spawned. This version of the DDA is gimp so no worries there. Actually, this event is EASILY one groupable. And this is coming from someone who is not raid geared (10.6k HP's 2k AC unbuffed and about 400 AA's). My resists are all 400ish and his effects never touched me. It did land on our cleric who was 73 and not sure what his resists were at. Hope this helps a bit!
Can prolly be done with a tank cleric and enchanter. Kill the 4 gimps first, then work the terror. Tank should get some agro on terror but don't get in melee range until it's time to engage, don't want the mob to summon. Be prepared for repops during the fight. If one pops while you are on terror then kill it. Have the beastlord tank. The dps on terror is gimp, nothing to worry bout.
Was able to box this with beastlord (tanking, 13k hp's buffed), 70 bard, 70 rogue and 70 cleric. Trick here is to use the leashing to your advantage and, as basicxp stated, stay out of range of terror until you kill the 4 gimps. Just worked on them one at a time and let the other 3 beat on me (don't bother trying to slow ones that are leashing) -- try not to damage them all or you'll start getting summoned all over when they leash. Cleric needs a bit of beefiness since he will be causing the loose adds to leash periodically.
Once you get to terror, best to pile on top of him on the platform since trash respawns will probably occur sometime during dda. Having your resists maxxed on your cleric here is pretty important as he will end up getting healing aggro from terror and spend a lot of time stunned if not.