Possible pyro nerf

Okay, here's my idea:
Pyro gets a slight nerf to its instakill that makes it harder to execute:
When a pyro hits a flaming target, the pyros exp bar fills up. An empty bar signifies 5 hearts true damage, and every hit after that to the same target in the next 3 seconds does 1 extra heart capping at 10 total. While this is happening, the pyros armor will slowly turn from red to orange to yellow to light blue, the blue being the instakill. The armor will then go back to red after the bar drains after 3 seconds.
This may seem like a big nerf, but think about it. A pyro will deal a 2 hit kill to anyone not steaking. This would rapidly drain steaks until the flag holder could get out of the flagroom, and combined with a ninja or two, you have something quite solid.
Thanks for considering.
-Inge
(Oh by the way red flames are the coolest, followed by orange, yellow, and then blue being the hottest, so that's where the colors come from)