Blood of the Betrayer woes. Ugh.

So, i finally got my 333 Shadowy Gems for the next stage of the rogue legendary quest - it's taken forever too. Anyways, i am now up to the Blood of the Betrayer - with additional stealth annoyances. 

I'm after tips for the stealthing part - and probably Nalice, if i ever get to her.

I first trying just stealthing through in Combat - as it's what i did for that stinking Creed, but it got me nowhere. So i made a crappy Sub spec (literally crappy, i just points in where ever, hoping for the best) and i have been able to get down stairs to the big room. I watched a couple of videos, and it looked like they had shorted cds on distract and vanish. 

Any help is welcome - i am very slowing learning how to Sub.

I'm getting very frustrated, i've been attempting this for about 90 mins - yelling at my pc doesn't help either.

Thanks,
Charamber, the sad/annoyed/starting to hate Zazzo/frustrated rogue who needs her new daggers.