Anecdotally found the main issue in Durnholde to be the 3 draknoid packs before the last boss, The melee have a 5k+ MS and the casters do a 6k voidbolt.
This in of itself isn't a big deal but the casters can also apply a 30 second debuff that increases damage done by 50% and damage TAKEN by 50%, getting this on the tank typically yields instagibs if you attempt to facetank anything not CC'd for it's duration.
[Edit] - Thrall has ~130k on Hc and can comfortably tank 1-2 melee mobs in the packs before the 2nd boss, his HP resets once he leaves combat so your healer shouldn't be wasting mana on him either.