The grendel is more balanced due to the fact it is a burst fire gun, scarb is a slightly improved scar that lets ya equip a silencer. I do agree though, but it may not be they are overpowered as much as most other guns are underpowered.
Sniper rifle- seems about where it should be
Shotguns- Utterly useless unless your within 5-10 steps of someone and they aren't moving (range too short, accuracy way off for a shotgun, slow rof in single fire)
The first SMG isn't too bad less dmg than scar but about as accurrate at medium range (at close range should chew up a scar but usually doesn't)
The second SMG has electro shells- pointless (these should have some sort of function-drain energy, slow opponent.. but doesnt) the flash from the shells alone make it difficult to see what your shooting, dmg is worst than the first SMG
Heavy Machine Gun- Slower rate of Fire than Scar, Less Damage than Scar, long reload, only bonus is its large clip but again one on one most often than not the scar is going to win
Grenade launcher- total joke, grenades do less dmg than frags, only one mode timed blast like the demo man in TF2, slow rate of fire, point blank shots do 0 dmg (really no impact dmg?!?!?) way limited ammo, direct hits even in pro mode are the only things to kill in one shot, shell doesn't always explode on a direct hit at range (seen shells hit a guy drop to their feet then explode killing em)
In most FPS the point of unlocking new weapons at higher levels is to gain access to better weapons really in crysis2 you only need to unlock 2 primary weapons Scar and Sniper rifle (3 if you want a silencer on your scar with SCARB). Alot of tweaking is needed here, shotguns need a bit more range and should simply own anything in front of it at that range, should not need the precision aiming of any other type of weapon to make up for its range/recoil and rate of fire on pump (which have anyone at crytek ever fired a pump shotgun, wow they aren't this slow). The Scar needs to be tuned down some. The first SMG needs a bit more falloff at medium range, The second needs some sort of function with its electro shells. Grenade Launcher needs a huge damage bonus, the shell explossion looks nastier than what it is, this gun also needs a secondary mode (on impact or proximity)- have to admit Grenade launchers are the bane of most MP FPS's because they usually come off overpowered but ya duh its a grenade launcher the balance for it is limited clip and overall limited ammo, mobility, accuracy and its danger of use at close range. HMG more dmg.
Lastly since we are talking weapons the range of melee and its dmg needs to be toned down.