You are shooting good team players that defrost. Which is a good thing and is a reward. Defrosting is encouraged. Three shots from an RPD will at minimum do 120 points of damage before modifiers are applied such as for stopping power. As does the M4 and ACR. Players cannot get that much health+armor. Except maybe care packages. I dont know what the server has that set at. Maybe consider stopping power or armor piercing rounds.
Standard hardcore is a pretty stupid mode if you ask me. What benefit is an AK over an mp5? In hc both kill in one shot. Even if you just hit a foot. Dont even have to worry about hitting the torso at all. The fact that there is now some defense, when before there was none, makes things more fair. At worst you lose 1 or 2 rounds. The other guy loses any armor he has and it doesnt come back.