On my rogue alt, I've levelled so far as combat-swords. I just hit level 52 and I had a couple blue daggers sitting in the bank, so for kicks I re-spec'd to ShS.
First I had to spend time leveling my dagger skill up in Searing Gorge (sidenote: apparently pickpocketing is tied to weapon skill, because I had it fail repeatedly on green level mobs).
Now to my question: Can you actually use a ShS to BS combo on a mob? I could not get it work, the mob instantly turns to face me. I even tried using a macro. I mean the whole point of getting behind someone is to backstab, right?