Seph,
That approach has been tried, ppl simply scatter and turning the boss to only breathe on ppl was an issue in the past. I agree, we need to move the dragon and have everyone stay in the middle, even right after vortex. It just requires some coordination and trust that the boss will be moved and the spark does not die prematurely..and dps realizes that going all out will wipe the group when they are full buffed and the tank is not.
I am still game to give maly tries, but Uld just gives us better gear right now.