I'm probably alone in this but I ,personally, am not a big fan of Locking on a target. It severely tunnels your vision on that specific target and, while this might sound good on paper, there are several fights where it's important to keep your eyes keen on your surroundings at all times, and complete awareness of whats going on in the fight is key to not ending up tanking the ground.

That said, I'm one of the few players who rather use the "standard" controls on my melee DPS instead of legacy. This pretty much allows me to always keep facing the target and the strafe keys let me hit my positionals while moving from rear to flank and vice-versa. Back-paddling isn't really an issue as well.