My rogue is got 69 last night, and I'm all subtlety. I have zero problems with mobs, of course I'm more about the pvp performance. Haven't had a good test of that, since all the bgs I'm in now are full of geared up 70s. I've switched over to pretty much using hemorrhage exclusively instead of sinister strike - it does a little less damage, but costs less energy so you can build up combo points quickly...
So my current pve attack goes:
Preparation (+2 cp)
Cheap Shot (+3 cp - full now)
Backstab (sometimes can get a 2nd in before CS breaks)
Hemo (and repeat until back up to 5 cp)
Rinse and repeat