I find some very viable teamwork tactics with randomers are:
as shielder: stick your shield in the enemy's face, and let your mate do the swinging
as pole/2h: keep a swing chambered or keep feinting, that way you don't risk teamkilling but make the enemy block/consider blocking. Works as shielder too
as cav: BUMP EVERYBODY, THE WINNER IS HOPEFULLY A TEAMMATE
the human meat shield thing would most likely end in a suicide-by-TK the majority of the time