Pally, 3xFire Mage, 1x Holy Priest

Went to the AH to get some fire resist gear for the pally, so had 160ish fire resist with the pally FR buff. Didn't bother with FR on the other toons.
Put all your toons on the bridge facing the circle area
Kill the guards
The rider aggros
Kill him really quickly
Pally goes to the bottom of the bridge and faces the party
Dragon lands and aggros to the priest immediately on the bridge
Consecrate and Righteous Defense the priest while facing the priest, what this does is face the dragon away from your party and therefore they don't need fire resist

Kill the Dragon, I have fire mages so I used frostbolt and arcane missiles while the priest heals when absolutely necessary
Loot and breath a sigh of relief
I used SoW and SoL when necessary, Aura was RD and Shield had a mithril spike, didn't have any problem maintaining aggro.
Alts ended with 100% health and 20% mana
Pally was at 10% health and didn't use LoH