No other class gets a save from crits, I don't see why the pyro should be special. I think it would be more suited for a class like scout or spy, which have so little health. And the backburner has completely negated the spy's backstab ability as powerful and original, because now pyros have it too.
Scouts and Spies are fine, they are deadly in ambushes and flanking, because they have the tools to do so. Scouts have speed. The run up close and quickly deal large chuncks of damage with the scatter. They can eliminate a key target and run away. Spies have cloak and disguise. While not having a powerful close range gun like Scout, they have the knife which kills from behind. You appear behind someone's back and do stabbing. When they get aware of your doings - cloak and escape.
Now, Pyro...he finds himself ambushing an enemy group. You know, offensive classes with Medics, for example. They have their backs turned. By flaming them he will not do enough damage to prove effective. If anything, he alerts them. And then what? He has not tools for escaping. He dies. That's how the situation ends usually.
Now, here is the problem - Valve describes him as a master of ambush CQC. They were thinking what to do so he can be one. So the ideas are:
-front ambushing: flamethrower/backburner + axtinquisher and abusing the slow back pedal of Heavies and Soldiers. Flamethrower has air blast. Good if something goes wrong (pushing them back with air blast) or finishing them of with their own tools (deflecting with air blast). Backburner sacrifices air blast, but gives extra hp so you can hang in there more while axing.
-back ambushing: backburner. Hmm, let's review the ambushes here. Scouts and Spies rely on big damage and escaping tools. That's great. Heavies and Soldier rely on brutal power and tanking. They can kill in matter of seconds and even if someone manages to turn...they still have the hp to take them down while being damaged.
So...giving the Pyro more speed? Nah. Cloak? Uhhh.
That's right. Brutal damage and tanking are the way out. Damage that's comparable to Heavy and Soldier. Something that won't give chances to the ambushed enemy. The crit flame!
In the heat of action people aren't going to be turning around, like when you are going for that last capture on dustbowl. Then, some pyro is going to run up and backstab your entire team with a spray of flamethrower. And in a close quarters fight, you might as well back against a corner so you won't get hit by crit flames, otherwise you will be hit by them at some point in the fight. But when you're in that corner you will die anyway. Think about all those times you get in melee fights with spies and they pull off lucky backstabs. Now multiply that chance by about 50 and that is the chance you will take crit flames in a fight.
If it doesn't fire like the rocket launcher, I don't care. Otherwise, overpowered and defeating purpose of pyro.
At one point I would have said the axtinguisher will be like the new knife, however, with the backburner, I don't really need to worry about it anymore. It is fine and other than the cool taunt that will probably come with it, nothing amazing in comparison.
We can argue here. I can say that no matter how aware is the player, he finally gets caught into a situation when he's shooting enemies ahead and just forgets about his back. This is the situation for Spies to go and get an easy backstab. The situation when practically anyone can sneak up and kill the target.
So it all comes down to Medic and teammates. With mikes. I play on iO servers from time to time. I often get Medics. And they are CONSTANTLY looking around, even in the heat of the battle. It's their job to watch for ambushers, no matter the situation. You are shooting, you cannot. They heal, they dodge rockets, their infrom of danger.
And I don't see why you complain about Pyro having an ambush attack smilliar to backstab. I mean, let's get this once again:
Scout - runs in, pops you with the scatter for major damage. He still can't take out the whole group, BUT he can eliminate the Medic almost instantly and get away with it. It's 2 shots to kill a Medic at close range and 1 to kill with backstab. Deadly as backstab.
Soldiers - they get behind the guys, they get the chance of direct blasting with the rockets. That's 2 to kill the Medic. Pop in the other 2 to the patient and finish the work with shotgun. And we all know the infamous crit rockets which are 1 hit kill in most cases. Deadly as backstab.
Heavies - that's my #1 point here. He does insane close range damage. His back ambush is instagib. So look, the backburner Pyro was in the game the whole time - he was called "Heavy".
They basicly gave the Pyro the ability to pull off a Heavy ambush in terms of damage, as long as he can sneak up. He was designed to wreck havoc in situations like that. As the CQC class. Now he finally can.
See, this is the main complain on the steampowered forums - Heavies/Soldiers/Scout/Spies, they are all better at ambushes. Now Valve decided to balance Pyro out by giving him awesome damage from behind. This is all good news.
And lastly, Pyro won't overshadow Spy in any way! Spies can go in the enemy base undetected and sabotage it. Destroy it's defenses from inside. Instantly kill and escape. Sap sentries. Take out Snipers. He can use cloak for quick escape. What if the new Pyro fails his ambush? He is either killed or forced to escape. Then you hear the nice "Pyro going this way!1" over mike. They will hunt him down. Detected Spy can cloak. He can lose the pursue by faking the direction he is going while cloaked.
Skilled Spy > skilled Pyro. The uptade won't change it. It also won't help him in mindless charging. It will help him in ambushes. You really think it's bad thing to do for a class like Pyro? I say it's awesome.