I'm talking about balance, you know the entire original premise in Team Fortress Two, as stated within the Developer Commentary? All critical hits do NOT achieve a state of balance. Just because somebody can live for a long time, it doesn't mean that all critical hits are balanced.
Let's discuss balance. Soldier is capable of one shotting eight out of nine classes with a critical hit, the same applies to Demoman. Sniper can one shot all nine classes with just a body shot. (This is probably one of the reasons why you were told to go play Call of Duty.) All critical hit servers ruin the team aspect of the game for me; one player is capable of single handedly pushing forward, destroying the entire opposing team and achieving an objective. (I.e. intel grabbing.) A Demoman can spawn camp for a good few minutes when there is only one exit from the spawn and he will never be in a scenario where he won't be able to lay down Stickies because he'll only require a third of the Sticky Bombs that he would usually require to pull off this tactic. A Sniper can kill everything with a body shot and thus, this makes the Sniper Rifle irrelevant and the Sydney Sleeper the better choice because of the additional 25% charge. In fact, all critical hits make a lot of weapons irrelevant and Underpowered, like the Backburner, Jarate, Bushwaka, Kritzkreig and so forth. You cannot seriously think that this kind of play is fun or balanced when you weigh up all of the cons.
Also, I never said that I wanted a twenty second respawn timer. I think that the timer should be different based around what map and team you're playing on. (Obviously, or I wouldn't have quoted that post.) My quirk is with Instant Respawn; it's awful when you're trying to capture the last point or push the cart to its final destination when enemies keep swarming out of their spawn. Ten seconds is usually enough and it encourages the teams to move out together and not by themselves, thus increasing their chances of survivability.
Finally, Medic isn't vital in all Critical Hit servers. I don't know what you're smoking, but Medic won't be able to rack up many assists when he gets one shotted by everything that isn't a utility weapon and when he doesn't even have a small hit box like Scout. The only thing that a Medic can do is over heal Soldiers so they aren't one shotted by Crockets and it's not like he'll even get a point for doing that. Medic is not encouraged on all critical hit servers because your chance of getting Uber is near impossible and you'll be lucky to get a quarter of the assists that you can get in standard play. I almost always top the leader boards as Medic in standard play, but when I play on an all critical hit server, I can't even get to the middle of the score board. I wonder why?