Flag returning is really where multiboxers shine in warsong IMO. I tried to play the middle a lot and escort the flag grabbers. Don't just sit around farming HK's, but work the flag carriers on either side and dont sit in the middle (you'll get graveyard zerged sooner or later). Warsong is my least favorite BG by a mile, but I do think a premade would make life easier in there for any multiboxer.

Something else I started doing for PUGS was pre-game I would tell everyone "Yes, I'm playing 5 guys at once. Please dont hang around me as you would be more useful elsewhere. I'll be doing XYZ and you guys should do ABC and I'll assist you where we cross paths in the middle. Yell out in /bg if you need me somewhere."

This works well in AB too, especially if you can get your own guys to come behind you to defend what you just took so you can move on to the next. Sometimes just saying crap out loud settles people down and makes it not such a circus to have a multiboxer in the BG with them.