I honestly feel like 4v4v4 is ok and 4v4 would be nice. A 1v1 arena would be cool instead of just duels. 2v2 and 3v3 would be nothing but frustration though without being able to queue with friends.
Too many times I’m in BGs (deathmatch specifically)try harding just to go 8-7 because I was the only one on my team putting in work. Or two manning and carrying two carcasses to the finish line only to lose because the other team of fully competent players made a late push. Just the other day I had a complete potato who let the healer get a kill before he did. He was 0-7 before stealing 3 out of 4 kills he got in the final seconds.
Imagine being by yourself with one of those in 2v2 or two of them in 3v3? I can’t speak for the other modes because I mainly play deathmatch but I take pride in a positive K.D even if I lose, I feel compelled to jump back in when I go negative. So I hate nothing more than going negative because my teammates spent all game respawning while I was getting spanked by 8 other players.
Any 2 team mode would be great at this point. It's been requested so many times on the forums so I hope ZOS adds something at some point.