To the OP, this might be late as ur friend is ignoring u now but maybe if u have a chance u can let him know some ideas i have.

Taking sethekk halls don't need u to be prot. No need to respec.
I think it is more on playing style.
Watch his playing pattern and tell him (if he is not doing)
(1) Taunt is his best friend. Loose aggro? Switch stance and spam it to get it back. (i presume he is not in def stance since he likes dps) All mobs are tauntable there. so he should be able to use it (10sec cooldown if i remember correctly and I presume he has no talent on prot tree)
(2) Use skills like mocking blow / challenging shout etc. Cool down is long but better than no one wanna party with you.
(3) Since he is 70, if possible try get def above 490 which will remove crit form ur dmg table & and have at least 25% shield block. Shield Block removes crushing blow. But this is not a game breaker in sethekk halls and might be tough for him.
(4) Be more mindfull on the situation. Mobs on healers? Taunt! Hamstring mobs so they run away slower. Switch target when mob is below 5% etc casters will nuke it and chances are it will die within the next sec or so and move on to next one (more time to build up aggro)
(5) Must have the following :-) SHIELD. More armour = less melee dmg = less mana healers need. Unless u r an expert u can tank in 2-hander but i doubt this is the case. At least whipped it out on boss fights
(6) NEVER think too much of DPS meter etc when u tank. (U said he just wanna finish sethekk halls right?) Take back ur ego and just go get the loots (farming)
Party survival is key.
(7) Remember to switch stances Intercept and intervene is key for last boss fight.
Need to get it off healers after the AOE. Int and TAUNT (best friend)
(8) Bring pots. Lots. Rage pots armour pots, health pots etc
(9) Spams attacks like HS/Sunders etc.
(10) As a party CC well. Resheep / traps /sap. Minimize stray mobs.
(11) buy him a book on shapes and tell him skull in general = ur target. If all else fails tell him that if u kill mobs in the following order Skull - X - Moon - Square etc, u get more DPS. It is a hidden programming code from Bliz.

Bear in mind that no matter what, ppl are going to pull aggro. Mages...pyro/POM/pyro...ouch
It is how fast the tank get it back that counts. TAUNT!!!

-nub tank-