There are several factors that go into the history of HAV vs infanttry in this that get overlooked since the last character wipe. It all boils down to one statement as to why tanks were considered OP, and are considered UP now:

Players didn't used to take AV seriously

Dust 514 rewards players for specialization. While tankers invested 100% of their SP into HAV, they got better and better while there were so few players that invested in AV. As more and more SP became available, it only got worse. Tankers could pubstomp ambush matches all by themselves, even under the flurry of militia swarm launchers with nothing to fear. The occasional person with standard AV grenades or higher tier forge guns could pose a problem, but the rest of the tanker's team could manage that if they weren't supported properly. The tides of a skirmish could be decided by a well fitted tanker with 3 squad mates.

Was it imbalanced: yes.
Should tankers have been nerfed because they were playing their role as intended: kitten no!

Infantry cried OP and nerf, pointing the blame at CCP for the imbalance. Truth be told, they had no one to blame but themselves. If an effective counter so something exists and the majority of players ignore it, it shouldn't be considered OP or get nerfed. Tankers have been doing what they were supposed to all along: Get better at their field until they can be the most effective in that role as possible. If their counter to that role doesn't specialize to keep up, then tough kitten. There shouldn't be any special treatment.

Now, players are finally taking AV seriously. Just the other day, someone decided to drop a marauder into an ambush. Instead of everyone fleeing, I saw swarms of AV grenades, forge guns, swarm launchers coordinating to ruin that unfortunate pilot's day. When it got blown to hell, I smiled as the person who showed up on the kill feed was using a prototype swarm launcher. A few seconds after, the unfortunate pilot rage quitted before his flaming wreckage even disintegrated. If he had a squad communicating with him, or there was another tanker on the team to divide the damage between each other, the outcome could have easily gone the other way. As of right now, HAV need infantry support as much as AV need to coordinate with weapons to match or surpass the HAV's tech.
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Tanks are fine, if not a tad op. I've been playing for a while, and in ambush, I frequently end up on the wrong side of one or two tanks that basically spawn kill my entire team across the map. No, it's not 'cause we suck, or what not, we simply don't get time to react when the tanks are already there and firing at you as you spawn.

They are not broken, look at your fit, and how you use it.