That is false, it targets the player it perceives as the biggest threat in its lock on area.
I just joined a game, so I was 0-0 with 0 points and last place on my team. Immediately heard "Enemy Hind incoming" so I stayed whereI spawned and took out my stinger. I started to lock onto the Heli as it entered the map, and the second it got onto the map it shot at me and killed me just as I fired the stinger. It targeted me because I was the biggest threat at that time considering I was locking onto it.
So your theory is sort of correct, it goes for the biggest threat in its line of sight. That isn't always the highest scoring player, but it can be.
I agree. Deadmanshand is annoying as hell too but I die more from final stand because I will shoot someone and carry on with whatever objective is at hand but turns out i didn't kill the guy, I just put him in final stand. After I turn away from him thinking he is dead, he kills me in final stand. Or I shoot a couple bullets in him thinking it will kill him only to find out I put him in final stand but another guy shows up so I quickly fire at him. So either I get killed because of final stand or I get killed by final stand.