Seen a few posts asking about this fight for rogues plues a few people whispered me about it. figured it was worth giving some info from my own experiences. The video is by someone called Taffer, it very much helped me so thanks to him for that.
First things first, watch this video http://www.youtube.com/watch?v=2i9dCnqCc0g
Spec: http://wowtal.com/#k=xoeH1LxV.ala.rogue.R0uRlS
This or some variation of it. You must keep Enveloping Shadows 3/3, Imp Recuperate 2/2, Quickening 2/2 and ilusivness 2/2 to be able to survive the twilight realm. everything else is pretty much down to preference but i find this spec works best for me.
Abilities
Feint: Use this everytime its off cooldown, provides 50% aoe reduction for 8 seconds and can be used every 10 seconds.
Recuperate: Ensure this is refreshed to full 5 Cps as often as necessary.
Cloak of Shadows: when you first get into the twilight realm you will start to gain a stacking damaging debuff, you can comftably let this debuff stack to between 25-30 stacks before you need to use cloak of shadows. use cloak of shadows in a safe location and whilst it is active quickly use a bandage to help top your health off.
Sprint: this can be used either to get to the adds quicker, however you can also save it to get you away from boss abilities quickly.
Smoke Bomb: the add will also shoot at you, if alot of adds are up this can drop your health fast since the attacks are pretty much unmitigated, if you find yourself low health in this situation pop smoke bomb whilst killing an add to stop the others shooting at you for a short time.
The Fight
To enter the shadow realm i find it best to use a dazzling destruction puddle near to the stairs. once you enter try to stay at top of the stairs for 5 secs so you dont end up in one of the other dazzling destruction puddles which would one shot ya.
Proceed to start killing the adds one by one, for me about 2-3 backstabs will kill an add (depending on crits). make sure to use feint and recup as stated above. whilst moving from add to add make sure to avoid the blue orbs and also any of the bosses abilities as they still hit you whilst inside the shadow realm. Make sure someone outside is calling out where the shadow breath is going to be so you dont get caught up in this. An important thing to remember is to stay calm, this isnt like most fights where your trying to get super high dps numbers and you got a healer watching your back, your aim is to keep yourself alive whilst also killing the adds at a rate that will ensure no more than 2-3 are up at a time. in order to keep yourself alive you have to kill adds to refresh recup and feint so if you focus on staying alive the adds die as a result anyway.
If you find you've killed all adds you can simple attack the boss from inside the realm whilst you wait for more adds to spawn so that you can continue to use feint/recupt plus help out the dps on the outside.
If you find the debuff damage is still overwhelming you (it shouldnt be really) you can use prismatic elixer for +90 resistance for more damage mitigation along with a haste elixer. also be sure to take a health pot with you, just incase
The fight for you is basically all about being aware of your surrounding and using 3 key abilities to keep yourself alive whilst also killing a few adds along the way