Did Barbarians lack common sense teamwork tactics (I distract him,you backstab him)?

[Robert Vermaat]

But to claim barbarians only knew to fight as individuals and lack any sense of teamwork is a slap in the face against human nature because even untrained civilians who never been in a fight before could work together to overwhelm a much tougher opponent using basic "common sense" teamwork moves like my friend  rearchokes that jerk from behind while I beat him up.

Exactly, it's nonsense. Also the people who think of a scenario where enemies can 'duel a Roman soldier while other sneak up behind' have no clue about ancient warfare. At all. best ignore such 'theories'.