Pyro
Airblast
I would say that the strength of Pyro's airblast needs to based on Class's weight, so for example airblast is not going to affect Heavy too much,but will airblast Scout further away. But also maybe reduce the strength of an Airblast by 10%, this will make Heavy a bit more viable for Last pushes, since he can barely get airblasted away. Nerf for Pyro, Buff for Heavy
Reflected projectiles should not Mini-crit, it should do the normal damage when reflected, as a trade off, make projectile's travel speed faster and reduced self-damage by 25%.
Survivability
To increase Pyro's survivability, I would suggest giving the Pyro a new and unique mechanic, which is: Give the Pyro a 20% damage resistance from all sources from the Player that is burning so if you set a Soldier A on fire, you'll get 20% damage resistance from all of his weapons, but if Soldier B comes and he is not set on fire, you will not get that resistance. If it sounds too OP, then let the damage resistance scale down with time, Afterburn lasts for 10 seconds, with each second, damage resistance goes down by 2%.
Unlock
Third Degree for years has been untouched, as an unlock, it needs an improvement, I would say that it needs a rework, instead of damaging medic via hiting his healing buddy, it should deal damage to healing partner ONLY but reduce Medic's ubercharge by +-25%, if Medic has less than 25%, he'll get damaged as well, so Uber % works as a self-defense mechanic.
Heavy
Mobility
I think that his overall speed needs to be increased to 88% (which also means increasing his Speed while spun up) from 77%, so basically Eviction Notice's speed buff. And either completely rework Eviction Notice or make it increase Heavy's speed even more, up to 95% .
As I said above, reduce the airblast strength by 10% while ubered, which will barely move Heavy at all, making him a bit more viable for pushing on the attack.
Survivability
Playing Heavy against Sniper is one of the most unfun things, unless you have a Vaccinator medic or patience for the sniper to back off or get killed. So I would propose a Damage resistance to the Headshots while Spun up, a 20% damage reduction in Headshots (120 regular, 360 fully charged), that way it is much more manageable to play Heavy . To not make it too OP, make sure it doesn't stack up with Vaccinator's 10% bullet's resistance.
Just my 5 cents. Pls no hate.