Why do I see nobody complaining about headshots or backstabs?
Why do you think the huntsman was produced? Sure, it still headshots, but the point was it was developed because of a sense that the victim felt no connection with the sniper, or that they couldn't have avoided that death beyond not even presenting themselves at all.
But ultimately they are class related designs. Their weapons deal lesser damage than most but perform better under certain circumstances, ie headshots/backstabs. They are balanced with low base damage and low class health+vulnerability.
Whilst a soldier has massive health and the rocket launcher deals massive damage under most circumstances, and crockets kill even most overhealed classes. A single random crocket from some noob who only just joined a server and happened to run into a well executed assault can ruin perfectly good timing and team work that took minutes to setup.
Snipers and spy's are different, they need to work for their crit kills, especially spy's.
edit: Yes, there is a performance formula that increases crit chance. The more damage you do, the more chance of a crit for your next shot. I believe the max damage/crit chance was either braught down from 550 or down to 550 in X seconds. It was supposed to increase crit chances based on performance, as as it was, it was a rare occasion it was affected as such. Crits would normally be awarded after one had killed most of his enemies rather than during crucial combat.
