Agreed, in the games I played, I often got #1 running around capping, but it felt like it was shaky and the game could turn really fast, it felt a lot more stable when I was defending 3/2, but ended up 4th or 5th on the team, just getting that +5 every now and then.
I'm not sure everything you get points for, but it seems like you should get them not just for killing people around your own point but also for interrupting captures, and even just people canceling their captures when you're around. Just you being in the right place at the right time saved the point, who cares if you kill them. Granted, sometimes there's a crazy start/stop over and over that two players might exchange and obviously that shouldn't make your score skyrocket or anything, so maybe a cooldown on it...