I leveled my DK 110-120 as blood, no issues. Once at 120, I haven't had any issues with tanking content that I can attribute to my class, rather than the lack of gear. There's a few places where you get your shit pushed in, but that's common across all tank classes.
Its different from live - yes, for example you can forget about ever using bonestorm, since you'll basically never be in a place where you can safely pool 100 RP to use it for max duration. However, the issues with RP generation aren't critical for your ability to tank. You do find yourself dry on resources in challenging fights, but that's expected from brand new content. You can tank M+2 and M+3 basically right out of the gate, after getting a couple of heroic pieces.