I'm not big on the idea of slow paladin fight style pvp but one shot kills are just not a good idea. I'd like the chance to react. Even if it is a slim chance.
Same on the guy coming out of stealth and shooting you in the back. You really don't have a chance. Even the suicidal ones that attack a big pack of enemies seem to pick me out of 20 people.
I've got lag problems so I'd likely never win these encounters anyway. I get killed alot from fire where I duck behind a barricade and the bullets come through the barricade and kill me anyway. Hit detection is client side for the person firing. But I don't feel so completely robbed when I die to normal infantry. I could have done things differently.
Hell aircraft are the cheapest no talent farm in the game and they don't bother me because I have a counter: Lock on rockets. I rarely kill them but I can at least make them go repair for 10 seconds.