I like most scouts against pyros. Shoot, jump away, run from back, shoot him in the back, jump away and do it until the pyro is dead. Use Madmilk if you got caught of the pyro. Or just stand away with a sniper a shoot the pyro down. Watch out Heavies, from pyros with backburners!!! They will properly pop up from behind! Even Heavies dont have a chance against a pyro from behind with a backburner.