Attempted and wiped to Grummus a few days ago. Here is what I had noticed:
1. Rampage - Seems to be the biggest problem. He single ramps for full damage, thus making it very important that the ramp tank (we used an Invulnerability hammer pally for this) gets healed properly. Makes this event a cakewalk. You don't want healers getting squished by rampage.
2. AEs - Disease based, so cleric group heals should work to cure these. Takes multiple casts to get rid of it though. I tried healing with my cleric-bot on the other room through a wall, but I think I still got hit by the dot. At 665 disease resists, I rarely ever resisted it. Nasty stuff.
3. Melee output - At nearly 5k ac buffed, my level 80 WAR was hit for a max of 5.4k (non defensive). Most of his hits were between 2k and 3k though, and some lucky 4k+ hits. I didn't see any flurries.
We wiped at 5%. =(



Bone Spiked Crusher
Chunk of Decaying Cloth
Diseased Ratskin Mask
Fabled Malarian Leg Ear Stud
Fabled Pus Covered Beetle Carapace
Fetid Flesh Wristband
Ring of the Pox-bearer
Runed Lance of Gryme