Yes Stratholme is a pain.

Through trial and error I found that a lot of the other dungeons (Scholomance for example), you could still leave your slaves at the entrance, but would have to kill the mobs with your booster in certain locations. Most of the dungeons return back on themselves (although often at different levels) so using the minimap you can see where your slaves are in relation the booster and kill when close enough.

The other advantage of leaving the slaves at the entrance is they can zone out and then summon your booster to them. Particularly useful when there is no quick way to return to the beginning of the dungeon.