Yesterday we had a 4th bomber spawn, but it did so when the walker was in its vulnerable state almost right away after the 3rd bomber. I was able to tank it just fine until it blew up so it wasn't a problem, but that was still definitely a bug.
What we are still experiencing as a bug is Kephess 1-shotting tanks after breath. I and our other tank would continually die instantly after the breath was cast to his Savage Arcing Slash. It wouldn't seem to matter when we taunted Kephess off each other, it was just instant death after the breath. We tried during the beginning of the cast, right before the cast finished, right after, and every time there was nothing we could do. The 4th bomber, while an annoying bug it's still able to be handled, but Kephess bugging out and 1-shotting tanks is a wipe every time.
I'd just like to add that we've been killing Kephess for months, had no problem taking him down, and never experienced this until the last couple weeks. It needs to be looked at because there's absolutely nothing you can do to prevent or work around when this is happening
Make sure your current tank deals ZERO damage to Kephess from the time they get knocked back until they are ready to taunt him back again. Start up bubbles/heals on next tank early as they will get hit hard - they should be communicating when they are taunting so heals can fire up on them.