Like Freyyy said, while it hardly seems necessary with your ~3.5k enmity-potency from a Rage of Halone vs. his less than 1k potency Deliverance-Maim-Berserk-Fell Cleave, having a taunt last for a few seconds would probably alleviate this issue (and with it, most of the urgency and set up involved in tank swapping). That is, unless you used Provoke right after you finished a combo (Hard Slash next) and/or right before his first Zerk FC.

Sidenote: Here's looking forward to unique tank taunt options, maybe, eventually?