Comparing fights is always a tricky thing but generally speaking, the Totgc fights aren't too difficult.
Northrend beasts can be relatively tough if you have shitty dps, because the Worms and Icehowl spawn on a timer, if you aren't done, you probably wipe.
Icehowl itself is pretty straight forward, just don't have anyone dying to the charge, else you probably hit the Enrage because you lose the dps from Icehowl not getting stunned.
Jaraxxus, again, pretty straight forward but if your dps manage to press tab and kill the right target, it's easy going.
Faction champion is a pure brain check, has little to do with gear.
Twin Val'kyrs is the same, if you wipe because of a lack of dps, people are doing something wrong.
Anub'arak is a 100% healer fight, the only difficult part about this fight is Phase 3 and there the healers have to set up their UI properly so they don't heal the same targets.
Basically, if you manage to kill Northrend Beasts, you're over the hill and can kill anything up to Anub'arak.
Nevermind that in this entire debate about difficulty, the cooldown reset thing is actually quite massive, first because it allows you to make pulls back to back without waiting for any CD's and second because you can also stack Warlocks + Druids under the roof to have a ton of Soulstones and Battle rezzes.