For T6, I still think that's an awesome run time. I'd be super happy with 12-15 min runs.

A few things, if you are running fire, and not running the Wrathful protectors I'm kind of confused - they got a nice buff in 2.0.5 where they no longer knockback targets allowing them to pump out more dps. The others are the ones that did not have it in the build.
Dropping Piranhas completely is a massive dps loss. I know with 4 it was annoying but the CC doctor is already doing reduced damage, slap on Piranhas and swap maybe Gruesome Feast for Creeping death and let that character cast it whenever it is up. The Creeping death passive will allow the 15% damage bonus to stay on for 5 minutes. Which is much more effective than Mass Confusion's Paranoia, or in conjunction.

Honestly I'm tempted to try this build out but it really comes down to that one item for perma stun everything. You could almost throw in anything to reach higher DPS. Say a Wizard or Ranged Crusaders. Although down the road once you reach full Jade Harvesters sets, the damage is massive. Could even do a monk for their added bonus damage. Makes for some interesting combos.

Thinking further though, the way multiboxing shines in RoS is through having multiple of the same allowing you to trade good drops to other characters. More or less I might be saying a lot of nothing. Blah. Either way this is strong