I say the Phlogistinator is not overpower, now before you come at me with your torches and pitchforks, hear me out.
The reason I say this is because the pyro is now weak to literally every class in the game. With the normal flame thrower and degreaser, the pyro gains the ability to not only throw flames but to use explosives if used correctly. The ability to use a soldiers/demomans/medics/snipers/pyros/scouts own weapon against them is a feature not to be taken lightly. However, most pyros do not know how to reflect many of the classes weapons back at them in the first place other than the soldiers, so I will let a pass on that. But the Phlog takes all those powers and throws them out the window saying a big goodbye to them.
On another point, even without a team and with a pocket medic Shebby (No Offense) a phlog pyro is still extremely vulnerable to everything. This type of pyro can no longer counter its greatest weakness, soldier and demo, and leaves the player basically a sitting duck.
However, I think the Phlog is now useless, especially since the Backburner does the exact same thing, but can crit CONSTANTLY if hit from behind AND still has airblast, though at an increased cost. The Backburner is basically better in every way and doesn't require you to sit there for 3 seconds just to get blown up for trying to get crits. This is just my opinion though.