Rizlona TLP, Serpents Spine Era -
My group had been dormant since early Velious, but I logged back in when Serpent's Spine came out and played some catch up. Couple weeks later I'm at 75 with a mix of Plane of time, Theatre of Blood, and tradable gear. SK tank at about 11k unbuffed. Mostly autogrant AA + about 50 spent on each toon.
After farming the bones I was a bit impatient and no guildies were on, figured I could take this guy. Plan was to DPS the zombies then burn Vesthon. Started the fight but the zombie wasn't going down fast. Turned out it had 200k hp per parser. So after I killed one, I hit burn on Vesthon and he went down in time and spawned the Abomination at about 15%. Abomination seemed to be going down okay - I did have to burn staunch recovery on my cleric - thought I was golden at that point. Then suddenly my cleric was down with the Abomination at about 45% and I'm toast. Seems the no aggro spells from my SK were landing and I wasn't paying attention to taunt. Wipe followed despite some real effort from my ranger to play cleric. Monk and bard hung around a while using defensive disks and everyone was dead at maybe 30% health for the mob.
Figured I'd be farming bones again after CR, but lo and behold the Abomination had not despawned. So I have 7 lvl 70 merc guards at the doorway to Hsgara's house, the Abomination and 2 zombies left. Most of my cooldowns are gone but I might have time to split the mobs. I did the mercenaries 2 or 3 at a time. They were pretty standard lvl 70 mobs with ~60k hp. When it came to splitting the Abomination and zombies I was having some trouble. They were pretty well linked and pathed together. I decided to pull them out into the open area outside the building to and see if I could hang one of them up on a corner and split them that way. I decided to try to hook one or more of the mobs up inside of one of the dragon skeleton bone piles. After I faded, the zombies headed back inside, but the abomination just stood there inside the bone pile conveniently. One on one it wasn't a tough fight. SK got to the 40%s a couple times, taps didn't work at all, and monk/cleric took aggro several times since none of the aggro spells would hit. But, good ole taunt still worked and the fight was pretty smooth. 350k hp on the Abomination, max hit was 1310. Killed the zombies, who didn't despawn after abomination went down, for revenge.
TL/DR: Vesthon may despawn in 3 min (I did not verify this) but the Abomination does NOT despawn for at least 30 minutes after it is engaged. So if you get killed by the abomination on the first try, you can go back and try again.