I haven't seen anyone mention this bug yet. I was in a group with my son, both in the same instance, and we had varied timers counting down the fight. When his ran out, several people in the instance just vanished from the fight. I put up a bug report about it already.
http://forums.defiance.com/showthrea...r-instance-bug
If you see this, please chime in on it. The sooner and louder it comes to light, the quicker they can fix this.
The warmaster is certainly a doable fight. But not if this kind of thing happens.