It's just a terribly made game, in my eyes.
My issues stem from these:
1) Programming issues. I've been shot and killed through more than six feet of concrete, by a guy using an smg. Physically not possible, no matter the caliber of the smg, no matter whan perk is on, I've tried.
2) While Grenades are programmed to explode in all directions, if there's a tiny little ledge that is two inches above where your Semtex grenade sticks, the guy basically leaning over that edge like he's trying to look down the buildings shirt an ogle it's goodies will not take damage from the explosion because, evidently, an inch thick wooden wall is indestructible.
3) The RC-XD only explodes outwards, despite being nothing more than a brick of Semtex on wheels, meaning that if you're standing right on-top of enough explosive material to convert the entirety of your body mass into a fine red mist, you'll be completely unharmed.
4) While they work about 6 times out of 10, many of the perks are untrustworthy and their limitations are poorly defined. Such as me firing at a stack of crates roughly two feet thick and killing the guy crouching behind them, yet not being able to fire through the inch thick wooden walls of a building in the same map, despite the embarrassing amount of rounds I'd just fired into the bloody thing. OR the fact that I've shot-and-killed several dozen players that had appeared on my radar, despite the fact that they were quite clearly using the Ghost perk.
All in all, it's terribly made, and the designers should be ashamed of themselves for NOT NOTICING those, quite blatantly obvious, flaws in Beta testing.