I play a thief conjuror, and it works very well. Here's how I do it:
I approach a room (or other aria with enemies) in sneak mode. From as far away as possible, I summon my antronoch into the room. Immediately any enemies in the room will partially detect me (eye a tiny bit open) so I move back further into the hallway, around a corner, or behind cover. The advantage to this is that I can see exactly how many enemies are in the room on my compass without actually entering the room. That determines my next strategy.
If there are several enemies, I wait until I am completely undetected again and summon another antronoch.
If there's only one, but it kills my antronoch I summon another one into the room and sneak forward and watch the fight long enough to see how much health it has left, than hide again. I keep doing this until my antronoch either wins, or my foes health is low enough that I can do and instakill backstab.
If my antronoch wins the fight, I go collect my loot.
There are a number of variations, but that's the basic strategy. I find that it can be very difficult to sneak in and backstab during the fight, but I've occasionally pulled it off. If you use ranged, you can probably pull it off a little better, but be warned that the target and anybody else will probably detect you after the first shot. If you do get detected but they're busy fighting the antronoch, you can sometimes get far enough away that you'll be undetected again. If you use the conjured weapons, make sure you keep them up or summon them while the enemy is fighting the antronoch, because If you cast a spell within a certain range of an enemy while stealthed, they partly detect you. They also partly detect you when they engage the antronoch. However, if your far enough away, they will undetect you during the fight. If there's no antronoch, there's a good chance they'll come looking for you and find you- though that does make for an entertaining way to lure an enemy around a corner into a backstab...
Other things:
Don't bother with necromancy spells. You need to be able to summon a pet next to an enemy that hasn't detected you, and your not likely to have any handy corpses in the right place.
The antronoch wont engage any enemy that hasn't detected you or attacked it. However, if an enemy even partly detects you, it will attack them immediately. So summoning an antronoch next to them is better than keeping one out. Doing both is even better- if your sneak is good enough, they'll probably go for the antronoch without seeing you.
Thanks to the above, this is not a very good strategy for dragon killing. You'll usually just have to duke it out with them normally.
This combination is a little technical, but very fun once you get the hang of it. There's a real sadistic pleasure in seeing the enemy run around looking for you once they kill the antronoch, and then summoning another one right in the middle of the bunch as soon as they let their guard down
Note: Yeah, yeah, my spelling's awful. I'm dlysixic. Cope.