That's true, CS:GO has become a lot worse in the last year or so. There are definitely problems with the simulation engine. It's really clear to see those problems, especially if your opponents fire 3-4 bullets simultaneously, you know that your simulation has been lagging out big time, but the system doesn't show it, netgraph doesn't show it, etc...
I'm running it on an FX-6300 @ 4000-4300 GHz for the moment, a Phenom II X4, my backup system, would probably have better single threaded performance and might squeeze out a couple more fps, but I'm totally happy with my fps for the moment, which is always between 200 and 300 in CS:GO in 1080p. A CS:GO pro team I'm very familiar with, uses the latest and greatest Intel octocores, and get about the same fps. The difference is in the tweaking. On an AMD system, you would typically get the best performance by setting the thread count to the CPU core count in the launch options, whereas on an Intel CPU, you would get the best results by setting the thread count to the total thread count minus one core (two threads). It's pretty amazing in my opinion that the difference in fps is greater by manipulating the thread count in the launch options, than by adding a shit ton of processing power (core per core, a modern Intel will have about 50% more ppc than an AMD core, and the Intel has 8 cores/16 threads, whereas the AMD only has 6 cores/6 threads, so that means that the Intel has twice the processing power of the AMD).
The good news is that we're approaching the end of CS:GO, and that the successor - properly optimized for linux instead of nerfed for linux - is around the corner. In the mean time, the competition is dead anyways, and now that the NA teams are also going to be checked for drugs, and C9 will have to do without Adderall, the commercial support for pro CS:GO competition is going to fall back also, so the whole scene will experience a total refresh in my opinion, making more space for the next installment of CS to gain momentum, something that CS:S for instance never had. What remains is the entertainment value of the game, and in my opinion, those software bugs, cheaters and general obnoxiousness of the recently added hype crowd to the scene, are annoying, but they're not that bad for the general entertainment value of the game. Even with all of the bugs, the stupid Valve policies and the corrupt MLG scene, CS:GO is still one of the best PC games, not as good as 1.6, because 1.6 was a game changer, but there aren't all that many games you could spend thousands of hours playing without developing a profound resentment for the game at hand... CS:GO is still CS, the version with extra lard and useless trimmings, but it's still CS.