Don't get me wrong, Mutilate is a great spec, and your build looks fairly solid, but I have a few... concerns.
First of all, Improved Kidney Shot is very lackluster IMO, I'd take those 3 points and redistribute them, preferably in Blood Spatter, which boots Rupture damage. Same goes for Fleet Footed, which I just dont see being viable in a raid situation, and only marginally useful in PvP.
Yes, there are a handful of very good talents early on in both Subtlety and Combat. You put points into Relentless Strikes and Opportunity, and I see no failure in logic behind that. The problem with Combat is that there are a LOT of filler talents, Improved Kick, Sprint, Endurance and Nerves of Steel, to name a few, regarding raiding. Subtlety is my favorite Rogue tree, but it takes a while for it to get good, you really have to invest a lot of points in it, because for Subtlety to work you cannot pick and choose your talents, it works as a whole.