Anyone that doesn't get killed more than 1 or 2 times in a game is probably not contributing enough or is playing against poorly skilled opponents. Or possibly you could manage to keep your tank alive for most of the game, which I have done now and then. But in that case you usually have engineers to repair you, and they often sacrifice their lives to keep your tank healthy. Without them your tank wouldn't last, but they will have higher death rates... who's more important in the rankings?

What about people repairing the base who may only get a couple of kills but die 20 times? Are they not good players?

The game is simply not focused on killing people, but instead on destroying buildings and vehicles. Otherwise, kills would be worth more points and would have more effect on ladder points. Anyone contributing to those goals will likely move up quickly in the rankings, unless they are unlucky enough to get stuck on the losing team more often.

The main flaw I see in the ranking system is that people in large games get a lot more points than people in small games. Someone that barely did anything but was on the winning team in a 64 player game could easily earn twice the ladder points of the MVP in and 8 player game (assuming they're on the winning team of course).

I think I'm ranked about 600 or so right now, although I don't know how often they reset the rankings. It's nearly impossible to play the game well without getting killed. When my vehicle gets destroyed, I usually run up to the nearest enemy target and throw a timed C4 on it before I die. Or if friendly vehicles are nearby, I'll repair them until I die. Getting killed is also a very quick way back to your base if it's under attack or if a beacon is placed.