I have the FX-8350 also, and unless I keep Steam/Blockland as the program in focus, it'll load slower. It may be some sort of 'optimization' via the AMD driver/overdrive. Any script-based GUI animation also runs at about half the frame rate if I have another program focused, so I'm guessing it gives it less cpu time. It could be AMD/FX specific, but I'm not entirely sure.
Although, I've noticed that it either decides its going to run fast or slow once and then sticks to that speed for the entire time the program is running. If I wait the few minutes for it to do a "slow" load, any function that involves the file system takes much longer than it should and causes the game to hang; if it loaded fast, all is good.
I'm not sure if this is the same issue, just noticed you mentioned the same CPU and the fact that there's ridiculously long load times. Generally if it takes more than a minute I just kill the process and try again, making sure I keep it in focus.