Hmm, I hear a lot of objections but I'm going to play devil's advocate and say that a higher ilvl minimum isn't as stupid as it sounds. Even hitting the dragon with every missile, plenty of cannon fire and explosive barrels, there's a good amount of regular old fashioned DPS that needs to be dealt before the beast goes down.
People seem quick to ignore that some of the monsters are 'on rails' as they gun for the cannons. As a tank, you can get their aggro icon bright red but they'll still ignore you until they reach their destination and fire their attack. Two options here. Run over to the critter for a stun (dragging any tag-along) or ignore it in the hopes someone else will stun it. It'll come after the tank once it's skill is done.
Furthermore, that giant turtle can be stunned, but as with all mobs he becomes resistant fast. He uses that move more often than you can stun, so he'd best be dead by the time he's ready for a 4th round.
There is certainly an element to a DPS race in this fight, and a level 90 character is at a severe disadvantage, make no mistake. A level of 100 isn't that big a leap in the grand scheme of things, but it will make a big difference to the fight.