5:1 ratio? you're talking about wow-pvp in pug's on battlegrounds right?
there is no ballance-mechanic that could close the gap between a well attuned team and random players in wow... or any other game.
i'd say there's nothing at all to fix ballance in wow. besides the arena wow's pvp suxx anyways and even the arena isnt ballanced.
mainly caused by class-imballance imho.
i think teamplay will be the key to success in fbc too and its most likely that some fights won't be ballanced due to the players-skills.
pug's (without a voicetool etc) will never stand a chance against a decent team with tactical positioning, good heals, telling targets, switching / spiking targets.
if your enemies team managed to kill 3 of your mates in a rush those buffs won't make any difference... you would probably lose with or without them.
EDIT: OR you just cc the enemy healer and switch on the player who got the killing blows to take him out asap - problem solved.