The only fix I know of that seems to work, is to have all of the players in their own respective parties, then the ADMIN makes room on the one team, then we all leave the game.
Jon the game with your party, and the team that has the least amount of players, should populate with both parties. . . . although it still depends upon map load if we end up on the same team.
Example:
Party 1 = Crushing, Deciph3red, PB82, and FesterTaint.
Party 2 = Dragonslayer, Darthnater, GothOrchid and TheN3wGuy.
ADMIN will need to make room on Team 1 for 8 players (probably 10 or so because it will fill the two spots before those folks can get back in.
Basically, to make this work, you have to have 2 parties. . . . and kick everyone on ONE team to make room for them (8-10 players). Once there is room made have the one party join, then have the second party join on a player from the first party.