It seems, however that the main issue being presented is the lock on system. From what I am hearing, HAV and DS pilots would have no issues with the swarm launcher if it was a skill shot, not a lock on ability. So here is a couple ideas.
1) Swarm launcher users must MAINTAIN the lock during missile flight or the missiles fly off in random directions and don't hit ****. This eliminates the set and forget system. This also eliminates the issue for us swarm users to have to constantly re-lock onto an enemy vehicle. We launch our missiles and keep launching them until we run out of ammo. However. We have to maintain the vehicle in our hit box or else we lose all the missiles that were launched. This makes our potential damage to vehicles much higher, on the grounds of killing them. However, it's a risk vs reward system. If you get killed, or you are forced to move because of enemy fire. Tough ****. The tank got away. This also rewards DS pilots. If the pilot out maneuvers the lock or simply gets out of range of the lock, then the threat effectively disappears for a time.
2) Vehicles get notification when they have been locked on. This will give the drivers a heads up to find cover or start moving.
3) Reduce the clip size of Swarm launchers to two missiles per mag across the board. The vehicle pilots should fear AV infantry, but not a single AV infantry. I anticipate that if all three missiles launches (from one person) were to hit, then a vehicle just doesn't stand a chance and is now nerfed to the ground. Killing a good tank pilot with good gear (i.e.an Expensive and rare investment) should be doable, but not easy. Realistically, it should take a number of players to take out as strong HAV completely. Having two missiles in the chamber will allow one person to at the least, fend off a vehicle from the team. Having multiple av players just means the anti personnel capabilities just went down the toilet, and the battlefield is balanced.