Not really, if I blame anything (I do) it's the level designs. If you look at Left 4 Dead and how well it's designed to have enemies rush you in ways where you have no cheap place to hide, you just know it was made for that principle game mode. The levels in gears 2 multiplayer are all really awesome when you play them in the other multiplayer modes, but the various enemies you encounter don't seem to have the proper AI to tackle your cunning skills of hiding in one location that they fumble trying to get to. Like, in one stage the big enemies with a mace got stuck walked towards me despite being on lower ground, then he got in some sort of loop where he would just walk back and forth letting me easily kill him with my pistol. Then you can even make use of the dumb AI there by placing those cover shields in walk ways and make an impenetrable fortress for your team.
It's a cool concept and still entertaining, but it feels so half realized and lazy compared to everything else.