[Sirensis]

I think the developers allready got that in mind, and how to prevent it. Severel ways to do that.

keep it in a locked of area, so to open a door you have to be on the quest, and noone on the other side. Or "lock" the fight to prevent assistance.

But I haven't found any information so far on how they plan to do that, though I am most certain they will have it figured out before launch. It's not like it's hard to see the problems, and it's ramifications. problem is rather on deciding what way is best to prevent it.