I've been having the same problem... I have two or three bars during the match, but it's like my hits aren't even registering. If I'm lucky I can take someone else down, but otherwise it seems like everyone can hit me, but I can't hit them. I hope they fix the problem soon.

Same here. Today I had the drop on a player, shooting him in the back after unloading most of the clip from the scar into his back he turned around and dropped me in 3 to 4 shots. I'm starting to get really pissed off. I'm thinking of deleting everything and starting over and coming back when everything is fixed. My current K/D is .39 and I've never had a K/D that low. Looks like I'm back on Homefront for now.
Same for me as well. I put two entire clips of SCAR ammo into a guy's back once before he turned and killed me instantly. I quit playing B.O. because of this &$#@ and I'd hate to do the same here.
I also have never had a KDR below 1.00 in any game, (not a great player but I average between 1.30-1.80 for most games and that's with never sniping or camping), but I do with Crysis 2. If you don't have three or four bars you shouldn't even try to play. It will just frustrate you.