It's a rhythem. Burn until Frags are up. Kill Frags, kill terrors, burn DW, kill frags, kill terrors, burn DW, Kill frags, kill terrors, burn DW. If you don't kill him on the third burn, yikes, you better have cooldowns.
Also, there is no reason why range and healers can't all stack near DW. Mark a spot. The only people who should be moving should be melee/tanks. This way everyone is stacked for AoE healing effects, Barrier, Spirit Link, etc.
Also, after frags are dead, people can hit "dream" at least once before you see frags again, twice if their timing is tight, and it should be back up for when frags start picking people for shrapnel again. Individual damage reducing cooldowns should also be happening at this point.
Aside from heroic progression we are working on the DW achievement this week. We're starting with Nozdormu's platform first. Then Malygos next week. Then Alexstraza, and we're done.