There is a lot of information on this in this thread, but it's all over the place, so here's an easy to read guide for one of the best instances (imo) for transmog gear and, dare I say it, fun. It's a great instance. Note that I never raided here when it was current content, so I don't know the fights well. The instance itself is a bit of a maze but you should work it out, if not there are some youtube videos which serve as guided tours (I can't find the one I watched again though ).
There is one dps check boss (bloodboil) so you'll need half decent dps, I was kitted out in mostly 463 gear at the time. Having good knowledge of your dps rotation and knowing when to pop cooldowns etc to maximise dps is good. I did this as smf fury.
To make most of the instance trivial you should spec into Second Wind, the damage the bosses deal out isn't very high but it's enough to kill you in some cases. Most can't out-damage second wind very easily though, so it's your life saver in more than one situation.
High Warlord Naj'entus
Easy. Very low dps requirement (about 17k while not cc'd I think)
Easy, move out of the bad stuff.
Watch for the flying trash before boss, if it doesn't land you can run back out to reset it. Just run past trash up to boss. (you can probably take the boss with a few trash firing at you)
Shade of Akama
Easy, kill adds, kill boss.
Easy, his interesting mechanic doesn't happen when solo.
Hard. this guy puts a stacking debuff that us warriors can't get rid of (paladins can bubble out of it, boo to them.), if you don't kill him fast enough it will tick for more than enough to kill you even through your second wind. I did about 60k dps or so during this fight (using a flask and a potion alongside careful use of cooldowns at the start) and it got pretty close near the end!
Reliquary of Souls
Medium. This isn't actually much harder than the rest but you need to think a bit(!). Phase1 - easy, then after you kill the little adds P2 starts. P2 is harder, any damage you do will be reflected back and you can quite easily kill yourself. Don't use dps cooldowns, perhaps even go to def stance after building up a full rage bar on little adds, using your -dmg% cooldowns will help. Basically you want your second wind to tick your hp back up to 35% before you do more than white damage, do a little, let it tick back up. Rinse and repeat. Although not strictly necessary as his damage is low you can interrupt Spirit Shock to make things easier, it's on a 15sec cooldown now so just get ready to interrupt as soon as your pummel CD wears off. P3 - easy.
The Illidari Council
Medium, my health got pretty low... Move out of stuff, interrupt heals (Circle of Healing from Lady Malande) and go and hit someone else when she has her Reflective Shield up. Their health pools are linked so you only need to be hitting one of them.
After killing these guys talk to Akama who will open the door to Illidan's penthouse suite.
Easy. I actually wiped first time on this because the glave elemental things put out some very high damage firey stuff on the ground. Then I read that you can bypass it by standing on the grate in-between the two mobs. Was very easy on doing this.
And by reading this, you were prepared!
I will now be doing this every week until I can get my grubby hands on Illidan's sexy shield and maybe a glaive or two, none of which dropped, boo...
but at least I am now decked out in some lovely T6 transmog