If you have a pacify type spell, just pacify the mobs (which you can do absent LoS), then step into the room and tag the one you want. If you don't, then you have to get "creative".
One interesting point about aggro pulling that isn't immediately obvious (and yeah, this isn't about LoS, but whatever), is that there is a different aggro range for "social aggro" versus "effect aggro". What that means is that there is always a radius around a mob where if it's aggroed on you, it will pass that aggro onto any mob socially related to it. However, there is a larger radius around a mob where if you do something to it (like hit it with a spell) it will pass that aggro onto other nearby social mobs.
In many cases then, it's a matter of figuring out which mob to tag. Root becomes an interesting pull spell (ironic, yes). Say you have three mobs in a room. One to the left, one to the right, and one in the middle. If you directly affect the one in the middle, it'll bring both of the other ones. However, if you affect one of the ones on the side, that one will come and the one in the middle, but the mob on the far side wont get aggro. Sometimes, however, the pathing of the mobs will cause the one on the side you directly aggroed to path into the middle of the room, then out the doorway (or whatever) towards you, thus bringing the one on the far side. However, if you root the one on one side, it wont move and will only cause the one in the middle to aggro. But since that one wasn't directly affected by you, it wont pass aggro on to the third mob. It'll come by itself.
I commonly clear 3 spawn rooms with my wizard by rooting the one on one side, the taking out the middle mob solo. I then target the non-rooted mob and take it out solo. Then finally, I take out the rooted mob. Obviously, this doesn't work for all spawn locations. If they're close enough together you're going to get all the other mobs in the room no matter what you do. But sometimes you'd be surprised how by selecting the right mob to tag can make a huge difference in how many come after you.
____________________________
King Nobby wrote:
More words please