It works when playing on your own too… assuming a player in question is capable of being in the thick of the action and coming out on top a reasonable amount of the time. I won 7/0 in a session on Conquest yesterday afternoon with no one else in the party - and a number of times capping back flags was essential, and hugely influential in the game.
I was also stupidly trying to get vehicle damage with a repair tool as I spotted I’d had a specialisation that I hadn’t unlocked for Support. Jeez that was not fun. Well, other than when a well known bunch of flyboys joined and I kept repairing the AA and taking them down so they left… lol
It can be frustrating working with randoms for sure, but I’d still rather try and win games than protect a KD.
As for people marking and not moving… who knows.