Didn't someone post on Reddit a screenie of them winning Seize without ctually PVPing the enemy team, or close to it? In general, I think outside of a pure deathmatch type BG (which I wouldn't even necessarily be opposed to), it's probably possible to win all Frontlines matches without killing anyone, except maybe Secure/probably Slaughter. This might be an issue with three-team PVP too - if the other two teams want to just fight each other and not you, and you get more points for objectives over than kills, you could easily win by doing essentially F-all over the course of a match.

I liked Slaughter (nowhere for people to run to when nodes were down, so you just beat each other up), but it's inarguably the most hated of FL modes in this subforum.