They took it out because of all the cross-faction trash talking and the subsequent whinging by people about it. Of course after they removed it, everyone whinged instead that now they couldn't do that any more.
Originally Posted by Miltiades
Will they get the regular experience from these quests or would my character influence the exp gain of all others as well (meaning we'd all get less)?
I think XP scales on how much of the damage you do. So if your high level char basically does all the work killing a mob and your friend's low level char is essentially just there gently poking it, they may not get much XP. You could try drawing the aggro but not actually causing any damage. Or just healing your friend's char (directly or with a companion).