The fact that I don't feel utterly hopeless on today's battlefield suggests to me that the vehicle balance, while not as good as some of the outspoken tankers seem to believe, isn't as bad as some players are suggesting.

The main problem is that their domain on the maps needs to be limited. With vehicles dominating open landscapes, more of the installations and null cannon interfaces need to be placed inside facilities where infantry have a chance both to make a stand and to fulfill a purpose beyond playing tag-along with tanks. Vehicles should be supporting infantry, rather than infantry filling in holes where vehicles aren't effective. Most structures are too small, too open, and too simple. With better map design, infantry could dig in for a long siege where having vehicle supremacy would definitely confer an advantage but wouldn't dictate the entire conflict.

Take, for example, the three-tiered in-ground facility with the CRU on the second floor and the null cannon at the bottom. If this were re-designed to put the CRU at the top (within reach of vehicles), a supply depot on the second floor and the null cannon at the bottom, having a vehicle above would enable enemy infantry to capture the top spawn point, even while the defenders are still able to spawn through the null cannon. The supply depot could then be used to refit into AV to push back the tanks and re-capture the topside CRU. In this way a single null cannon is transformed into a three-stage conflict: (1) capture CRU to permit infantry spawn, (2) capture supply depot to cut off AV and secure topside position, and (3) capture null cannon. And this is not one of the largest or most complex facilities.

This is exactly where vehicles need to be: Vehicle superiority is advantageous when it comes to entering into a facility, but once you're there you will still need strong infantry--not just one or two players with the ability to throw grenades into foxholes. This separates the vehicle gameplay from the infantry gameplay to a certain extent, so that vehicles mostly fight one another and infantry mostly fight one another, but the overlap is significant enough that they both impact the ability to win any given match.

Limiting the ability of tanks to engage infantry solves nearly every other problem, and does it without artificially limiting the sandbox: players won't want to play tanks as much because there are a lot of places they can't go; teams with too many vehicles won't be able to take points as easily and will be unable to defend their points if enemy infantry manage to break through; vehicles will still be tough and still serve an important function in the game; and players could still viably do all-vehicle battles (provided the number of vehicles doesn't need to be limited for performance reasons).

AV still requires some buffs to be viable even in this circumstance, but in the current iteration we have to accept that infantry AV today is primarily about pushing vehicles back from a position and less about destroying them. With respect to this, creating tactical positions that are specifically useful for AV to fight vehicles will be important. These tactical positions would generally be elevated, accessible from inside a structure, and provide cover that is occluded against vehicle splash damage. These again increase the variety in gameplay by providing positions that are exposed to infantry but protected from vehicles--a map-based rock-paper-scissors scheme that mitigates AV players' relative weakness against vehicles but still leaves them open to infantry assault.

TL;DR: The maps are too open, so that if vehicles dominate they are able to dominate everything. Re-working maps to limit the ability of tanks to engage infantry solves every other problem, and does it without artificially limiting the sandbox or returning tanks to paper-thin status. Infantry AV still requires buffs that can be made partly through map design, but its role has fundamentally changed from destroying vehicles to routing them.