Yeah, I've debated that myself. Though I've never really taken a solid opinion on how/if I think that should be changed. The fact that I, well equipped, and on foot, can usually hold my own against multiple vehicles, barring a Goli, or Levi, does seem a bit odd, and can also be quite un-balancing if my team is making good use of vehicles, but unless they change the way vehicles are handled, that ability is almost necessary.
I see it needing to go one of two ways. If vehicles are beefed up to more consistantly take on lots of infantry: A) There needs to be much less of them then there are now. or B) There needs to be enough for everyone at almost all times.
Considering how gameflow in current onslaught almost makes fast manta travel from node to node a necessity, then maybe having beefed them up, is a bi-product of having less of them, and as well, making the "hoverboard" or something like that neccessary, so that even if you don't have the offensive power of a vehicle, you still have a means to get where you gotta go.
Just hope user maps account for these things.