why do two shield lobs? Just tag the dreadnaught the instance it spawns with provoke and shield lob, one should suffice to get the dreadnaught's attention then proceed with your enmity combo. Save your Off GDC skills for the dreadnaught if you still can't pull it off healers.

As for dreadnaught position, ideally it should stack ontop of Avatar in the middle.

tank at the Avatar's targeting circle, you dont need to move to pull the dreadnaught.