hmm...not sure how hard this would be to do, but could it be possible that when entering for the ToH that you're automatically placed in either a "light" guild or "dark" guild based on your allegiance. essentially the signup npc would unguild you (but save what guild you were in) and then put you in the properly affiliated guild, this way there'd be no real need for parties, save for maybe party buffs and you wouldn't have to worry about hurting your own teammates since you're in the same guild, there would be no friendly fire.
like i said, not sure how hard that would be to do, but just a thought.
