Well, most of the times you cant really say who is winning the fight, unless it's 2-3 vs 1. Pretty much all of 1vs1 fights are decided by single mistake. But yeah, when I see 5 vs 1 in our favor, I'm not shooting into that, unless the remaining enemy starts running away. Also, whenever I shoot into melee, I make sure that I either hit the enemy or noone, which can be easily done by mentioned observing the fight for 2-3 seconds.
I teamkilled 3 times, two of those were long distance shots into clusterfuck of 3-4 enemies and 1 of our melee, where I was so lucky to headshot our guy. The last one was just my sheer stupidity. Otherwise I shot a teammate maybe 5 times in my entire career as archer.