Now with solo tanking, there is no fallback, if the opponents decide to hard counter your tank, they can just do it (doesn’t mean they will win though). You will have a bad game all round, or you must enter the role switch game if you want to kind of play the game and win.
Every tank has some kind of counter, soft or hard. But for instance Bastion tends to invalidate lots of tank plays, that will push the solo tank player to switch all game (being hard countered by 1 player as solo tank, huge disavantage for the team). A good Sombra will be a force switch too for some tanks. Ok starts rein, switch winston, switch zarya, switch orisa… It doesn’t help that Hog is bad right now as for instance you can’t really delete an anti-tank with your tank now, without Hog reliable combo, Tank is just an ult box with the correct counter, you must rely on your DPS to kill the counter, to just PLAY THE GAME, or get deleted. It invalidates the idea that tanks carry the line and initiate actions (what is the real good thing about playing tank to my mind).
I really feel that contrary to popular belief, best dps pair is the most important advantage than tank diff, because, in fact, you can always invalidate a tank by switching DPS / Supports, and the tank will be forced to switch off. If they don’t switch DPS/Supports it means they are winning the DPS war, so enforcing the idea that they are indeed the most important role (well now supports invalidate lots of things too, maybe they are a big factor, but only if they enable real secure kills for their DPS, they rely a lot on them too).
The game has become a mess of always switching team (mostly for tanks or they don’t play the game) to my mind (except if teams get their mains to play and don’t wanna switch) and is a proof of the poor balancing right now. Hard counters will deny skill gap or even gamesense, forcing switching off.
Duo tanks were the backbone of Overwatch 1, as it builds the whole team and the frontline, solo tanking means if you get the best tank and a correct teamplay you win, but most of the time, teamplay gets really random, and securing kills is so important now with so many supports that deny picks, DPS seem to me the most influent role right now. I’m playing between Gold & Diamond by the way, depending on the role I pick. I tend to play more supports than tanks now but it is really sad, I would play OW 1 tanks anyday in place of this balance of 5 vs 5, and there is no way to go back to that.