Any idea on how how a Gunbreaker Rotation would be set up?

[BrokenFiend]

For short combats i think the starting rotation should be:

Bloodfest (90sec) > No Mercy (60 sec) > Sonic Break(60 sec) > Gnashing > etc... to take more profit on the DoT damage from Sonic Break.

Generally shorter combat will only be with Mob pulls, right? So, yeah I agree, but probably replace Sonic Break with Bow Shock for that AoE DoT and then spam the AoE rotation.

By the time only one mob is left, the whole party will be focusing it and Sonic Break's DoT won't last long enough to be worth it, most likely.