With all the drama here, I debated for days whether I should even bother posting, but the recent HMG buff actually gave me some hope for this game again. So I'll give it one more go.

It's enough evidence for me to know that tanks are OP because of the insane amount of spamming them on the battlefield. But I know that isn't enough for everyone, so let me explain further. Even mercs that are terrible team players, have little to no gun game, and no situational awareness are still extremely successful in a tank. Now put that tank in the hands of a player who is good at all of those things, and you have something that's beyond OP.

Why is it OP? You have created something that is technically able to withstand enemy attacks from an entire team at times (since most aren't even AV). It also has the ability to flee the scene at a high rate of speed at the first sign of danger. And it has the highest killing power of anything on the map. Any one of these is enough to consider it OP by some standards, but you have given tanks all 3. Imagine if an infantryman could run 10x faster than a tank, shoot it down in less than a second, all while being attacked by 3 other tanks and just shrugging them off. That is exactly how infantry feel right now, and that is why so many people are quitting. This is a competitive fps, and it should be played like one.

There are some good suggestions out there, and here are a few:

Return AV weapons to 1.6 stats. As a vehicle driver myself, I know how ineffective all of these weapons are at there current state. They've been nerfed to the point that they are just wasted skill points. Any tanker will tell you that Proto AV weapons with level 5 proficiency and stacked damage mods should be ineffective to a tank, but you need to use common sense and do what you know is right for this game.

Slow tanks down.... way down. Who decided tanks should be so fast anyway? In what world do tanks charge around the battlefield into the middle of every dangerous situation? Thrusters on a tank?! Did someone put NOS on that thing? I know this game isn't real, but there should be at least some small sense of realism.

EMP grenades - completely disable a tank for a brief period of time, leaving it vulnerable, unable to attack, and unable to retreat. only effective against vehicles. It sounds awesome, but I wouldn't expect something like that to be added until like version 3.0 or something.

Vulnerable point - maybe a small window to shoot the driver through. Not as bad as the giant open convertible that the poor LAV drivers have to put up with, but something that even non AV infantry have a chance at fighting back.

Stacking hardners - I understand that the active hardner should make a tank almost invulnerable for a short period of time, but my gunnlogi has 3 stacked and I can run them continuously with no cool down to worry about. This is clearly not as intended and the tank should be limited to 1.

Limit tanks to 1 or 2 per side at a time. During 1.6 and before, 2 tanks on a battlefield working together made an extremely difficult fight. Now that they are OP, 7 tanks per side is not uncommon and is beyond ridiculous. I personally would go even farther to say that you should only be allowed to spawn 1 tank yourself during a match. So if you lose it, you will have to wait until the next match to spawn another and it gives others on your team a chance to call in their own. Tank spamming should not be allowed.

Raise the price of tanks. I don't like this one. it's obvious, but it doesn't solve anything. And it just gives tankers an excuse to justify being OP. I personally like the low isk cost and sp requirements as it gives even new players a chance to try things out without a huge investment.

Increase the spread of all large turrets. This would essentially make them less useful against infantry, but still useful against other tanks, vehicles, installations, etc. The turrets are currently dead on accurate even from across the map. I've been hit many times by a rail turret from so far away that I could barely see it. You can literally shoot a rail turret tank from the blue side red zone and hit LAVs on the red side red zone in most of these maps.

Infantry only battle options. It would work, but I'm certain no infantry would join the regular battles unless they were running with tankers.

Edit - added 2 more ideas:
Prolonged deployment time for tanks. Make a lead time of some kind, maybe 1 minute after calling in a tank for it to be deployed. This would almost completely eliminate tank spamming without nerfs or buffs. It would give AV players a chance to eliminate 1 tank at a time without having that tank replaced in 10 seconds. It would give ambush players and all infantry a chance to establish themselves before getting dominated by tanks. It also requires the tanker to invest time to be the most OP person on the map.

Symmetric decrease of fire power and defense of tanks. this would allow the same tank v tank battles while making them slightly less effective to everything else and more vulnerable to attacks. This is really just a nerf, but probably badly needed at this point.

And FYI, calling in another tank to deal with a tank still leaves an OP tank either way and is not really an appropriate solution, despite what tankers seem to believe.