For a d/w prot build. If you choose to go the BT route, the next patch will have TM give a threat (10/20/30%) bonus to BT and MS, you don't need to spec defiance to tank, but it sure damn helps. It's hard to build a prot/fury build, unless your bypassing imp tclap, or loosing out on the top end fury tree talents.
But if I had a choice, I would consider something like
8/41/12 or
5/41/15. And depending on what your tanking alot...
You don't need to spec imp shield block (but it's still a very good talent to take) unless your tanking mobs that have crushing blows. Stressing the NEED and CRUSHING parts.
It's very difficult to balance that kind of spec.
If your not worried about mitigation/avoidance and just want to DPS tank, Arms/prot builds are also good. TANK WITH A 2H!
Ok, all silliness aside, as long as your not in a heroic instance, and your healers aren't asleep, you can tank most trash with a 2h in defensive stance. You should put a shield on for bosses.
I used to use a tanking build very very similar to this one
42/5/14.
Put on your bare minimal defense gear, and stack your dps gear next to it. (72 elite mobs require 485 defense to be uncrittable, Level 71 mobs require 480) resilience can really help with getting that crit % from trash mobs down. So consider putting on PvP gear. (with just 50 resilience you cut your required defense rating to 450 for lvl 71 and 455 for 72). Get the
Tank Points addon to help you figure out if your uncrittable.
In no way should you be tanking raids with these builds. Unless you have some really amazingly good healers, and great dps to push things along (read as: knowing how to read a threat meter). Or you have a huge gear advantage over your raid mobs.