Been so long since I have played CoD4 but I am pretty sure back then you got 2 claymores and bomb squad was the only perk to help you deal with them.
I think people need to harden up a bit, next the c4 will be too overpowered.
Hacker will do away with pesky claymores, or throw on the flak jacket and run past them smiling but seriously if they give you anymore ways to dodge claymores they may as well remove them from the game.
BF2 claymores were always instant death and no one ever asked for those to be nerfed.
Ghost pro challenges weren't that hard, just play on a normal server (non HC) and throw flash/concussion/gas at the first encounter each time you spawn and you will get each one in a few maps or so.
As for destroying a sentry gun, select sentry gun in your killstreaks and throw it to the enemy and then just wait.
Lightweight pro, Flak Jacket pro, Marathon pro and ninja pro I won't bother with as they require objective based awards and I don't play those game types.
I find the biggest issue is when playing HC friendly tags either don't show up early enough if at all.
Friendly tags can be blocked by a blade of grass hindering your view or a team mate emerge right in front of you from around a corner, which generally ends up with one of you filled with lead because their tag won't appear until they are in direct line of sight.
But for some reason you can see the tag of another friendly camping in an upstairs room or something across the map.
Makes for very frustrating gameplay especially if people are new to HC.