This would be a perfect plan if your group had some pets, but:

Try using battle shout (while in range of all friendly targets) for spammable threat. It does a funny thing in classic where you get additional threat for every friendly target it hits.

Also remember that dps/healers get an additional 20 or 30 percent threat if they're in melee range, so if you're using arcane explosion for dps that might be why your tank can't hold it.

Sent from my SM-G975U using Tapatalk