Just so you know, if your tank (tank 2) taunts too early (prior to the cast of Breath of the Masters), the other tank (tank 1) can taunt during the cast of BotM to prevent tank 2 from being hit again; if this happens tank 2 will again be laying circles. Our tanks do this intentionally on SM (we have a shadow and a vanguard). The shadow places the circles the whole time and the vanguard tanks the boss the whole time. it takes far more coordination to do intentionally, but it does happen on accident some times.
Well that was the problem, we were taunting too early and he was jumping back and one shotting the first tank. waited for the cast and easily killed him.
I first cleared that fight when it was pretty new, did it a couple of times and hadnt been playing since. i remember doing the taunts so the one tank keeps the circles and one tank just keeps tanking kephess but it doesnt seem like it would work now, tank1 is tanking him, tank2 taunts to early and he is going back and one shotting tank1 then going back to tank2. Have you tried that strat lately since they made some changes to the fight?