Hey, taunt also redirects targeted healing and buffing attempts, so you might want to manually control your healer’s ult.
Also, in the 1.10 update, this boss fight was slightly nerfed, and a new opt-in system was added that can make quest fights even easier. You can grab 1.10c off our Patreon for free. Tomorrow, we will release 1.10d (which also will be available here) with additional bug fixes and optimizations.