Doesn't really work practically in the current ecosystem. It only worked because of the pre-MoP class design wherein the majority of your kit was class-wide. Also, as someone who switched to DK for Wrath, I feel like the concept didn't actually pan out gameplay wise. The three specs felt extraordinarily same-y. If the concept were brought forward, it would look a lot like old Feral: very awkwardly pulled in two directions.
I do think what should be done is that tank specs should all get some talent in the vein of Gladiator stance; sharply cutting their defenses and threat generation and boosting their ST damage 25-30%.