i'm actually gonna go ahead adnd comment on this thread.
"Players that go all over the screen in a single bound, as if a plane were treated .. shot after another, all in the head ... characters made some kind of alloy steel, impervious to bullets themselves and weaknesses of a magnum"
google hl2dm movement tutorial. it will teach you how to strafe jump and move very fast in the game. also when you talk about people taking shots in the head like they are made of steel, in hl2dm suit helps a lot. also you may have not have shot them in the head, make sure you hear that headshot sound, theres no such thing as health hacks in any game that's popular. just google any game and health hacks you won't find anything. either the game glitched up, the server glitched up, or the hitboxes were messed up.
"errors that the game creates the blood but not giving you as good shot but all you have left a stain on the wall and the other player will go limping on one leg without his health marker alters the minimum being .... is this possible?"
yes, this is possible. it's a glitch in the game.
i agree that hackers really suck. most of the hacks i've seen people using in hl2dm were just spin hacks and they really couldn't hit anything. you guys have to realize that this game hasn't been updated since july of 2008. the game has many glitches and valve doesn't care apparently