Enrage is not due to death but rather time on the fight. How long was your kill pull? I haven't pull this mob in about 2 months but from what I remember the enrage happens at 8-10 minutes.
didn't see the named go enrage near the end there.. it might be caused due to alot of deaths that causes the enrage/dmg shield
We've found that if you've got the heals (EM SS gear should be more than enough) you can actually avoid the joust and fight through the sludge. Helps keep DPS up and allowed us to burn fast enough to keep her from throwing up the damage shield.
Interesting. You are right though and it must be a time based thing because she didn't do it at all on the second pull and we toasted her. Its very important to make sure people move out of the puke pile she spits on people as well. Strat is basically this:
Everyone Pile up under her rear end.
Engage and Burn.
AE tanks grab any adds that swarm in. Ignore them and burn the named.
The named burrows into the ground. Have OT's or scouts pull in all the groups of centipedes that spawn. Burn them all and once they are all dead she will unburrow. (While burrowed, she is immune to damage and heals herself so burning the centipedes fast is important)
Rinse and repeat.
She will red text pick one person every 45 seconds or so and spit on them killing them. Where they were, a pile of goo will be on the ground. Everyone needs to get out of it as it will put a uncurable nox dot on you if you dont move.
Once she gets down about 20% depending on how long it took you to burn her down, she sort of enrages. There is no message, but you will know it happend because people will start dying like a fail mechanic has been triggered. At this point, slow your DPS because it seems that there is a dmg shield or lash back type attack that she activates at this point.
Nope can't do anything special to avoid this except burn faster before it happens, it's the dps check for the mob. You can live through though; just tell your dps classes to cast one spell/CA then wait for a heal, cast one spell wait. And make sure you tell your wizards and warlocks not to use Thunderclap because it equals instant death =).