The issue with Dreadtooth at 5 stacks is that you need to have all Sage healers. The reason for this is because he throws an uncleansable DoT on the DPS that almost requires you to have Salvations thrown down to soak it up. A 24 man group cannot do this alone. A second group full of heavy range DPS and more Sages is required to sit back while the primary group kills it. I've only ever seen one guild try it. They got him down to 10% before they wiped.
So the mechanic we've got to focus on his DoT. What's the name of it? Maybe there's some datamined involving immunity/protection from it. Just got 4 stack DT down this week so any suggestions for 5 stack are much appreciated.