It sounds like you guys are killing the Dread then dpsing the Soldier and Knight while you wait for the next phase. I suggest switching that around, and killing the knight/soldier instead of the dread.

It puts a bit more stress on the main tank, but my FC has found it's a lot cleaner. Then, when phase 6 starts, your OT has his hands free for aggro, the MT just has to flash real quick, and then you can just kill in this order.

Spinner - Damaged Dread - Soldier/Knight - Bugs - Dread.

It also helps if the OT kites a bit while he waits for DD assistance.