viper is right, the class is fundamentally bugged. You can see in the gink video of him playing on gully, it flashes up with a "criticals 20-39 damage per particle". Well, since particles can hit more than once, this is not true at all. If this was the case, it would be more forgiving in terms of damage, and people would feel like they can outplay it.
This is main reason why pyro should be banned imo. From a competitive point of view it hinders player improvement/skill comparison, which is never good for a competitive game. It does this by forcing players to relearn how to play the game with the bug, and then forcing them to relearn how to play the game without it after the bug gets patched. This is why competitive games like league of legends disable characters with bugs until they are fixed (dependent on how gamebreaking it is).
There is nothing wrong with forcing players to adapt to new change, but if you force players to have to adapt too often, or too much in one leap, it massively hinders how you can compare skill from one player to another. Which is largely the point for competitive games, people want to compete against others and compare their skill levels.
Whether or not you agree that the leap was too big or not is ones own opinion, however there should be no disagreeing that pyro should be fixed in terms of the bugs it has, and the unclear visuals protruding from the flamethrower. Valve tends not to release updates too often for this game, so I don't have faith the bugs will be fixed anytime soon. That means it is on us as a community to fix the problem. The simplest, most viable solution right now is class limit 0.
Whilst pyro has it's place in the game and there is a lot of cool stuff you can do with it, the forced use of unlocks and raw dps of the class make it not only unenjoyable, but much worse for the strategy of the game. There are only two counters to pyro right now. One is a sniper with darwins danger shield, the other is a better pyro. I remember when wee booties got nerfed because if one demoman ran them, the other had to as well. Very similar scenario here since you can't always oneshot a 260 health machine running at you surrounded by a cloak of flames.