So... basically what you want is for the mob to stand there like a dummy with his back to you while you whack away?
That's how I got your post anyway.
You already mentinoed how backstab in two ways, either companion or stealth, what's the matter?
If you got their full attention, how would you think being able to backstab was possible?
*Stun them and get behind or whatever, it works fine as is, of course they will turn to you if you attack them and keep their attention. If you grab attention from your companion, just shed it.