TMP just used phlog for a large portion of a scrim vs a team I was trying out with, and it didn't seem to affect anything in a huge way. I don't think it's anything game changing, and if you see the pyro taunting, you almost always have time to run away.
I think that the use of the phlog could lead to maybe a few sneaky picks through out a game, but overall the pyro will be less effective.