What do you propose? We're quite good at it and it's not easy to counter.
The problem with 3-5-2 are the two WBs, who are essentially defenders. Sure, they'll push forward, but players like Kolarov, Zuniga, De Ceglie and Lichtsteiner simply aren't dangerous enough. And you can't use technical/dribbling wingers like Ribery, Robben and Nani, because by definition they don't know how to defend. Nor should they waste their breath running up and down the whole flank.
It's kind of a limiting formation, it forces you to attack down the middle, which can be a pain in the ass, if you don't have an AMF like Zidane, Ozil, etc. We make do with Vidal and Marchisio cutting through into the penalty area. Doesn't always work though. With Llorente and Tevez up front there should be a noticable improvement, but I still wish we'd switch to 4-3-3 from time to time. Hopefully with Pepe's return ...