Let me guess KingBibi, you didn't read what Elliot wrote.
Having two tanks some times was stated as being a bug. And it isn't a mode that is meant to be symmetrical.
If it were symmetrical, the map would never advance and every match would end in attackers losing. Symmetric is each side holding their position, which means an attacker loss by default. The purpose of the tank is to advance the match to the next objective. The goal is for every match to end at the last objective with a 50/50 chance of one or the other side winning.
They analyze the match metrics and adjust things to try to achieve an even win rate. They are looking at the data and are considering adding more stationary defense weapons to balance their previous adjustment, to hopefully prevent everyone from feeling they need to be engineer as a defender.
The problem with Breakthrough is the trash maps, so about the only easy thing the devs can do to try and balance things better is tweak the vehicles. The mode, and it's predecessors used to be amazing fun, but they have somehow butchered it
