If you're really serious about tanking, you need to go Prot/Retri. There's some preferences in details, though. I'm in favor of the 0/38/23 build to have nice aggro and receive 6% more healing to boot. I eschew Ardent Defender since it's a completely useless talent.
Some details about your build:
- Forget about Imp Devotion. It's really not that great, only adding like 0.5% damage mitigation.
- Work Toughness in somehow. The 10% extra armor will help your mitigation (and is way more efficient than Devotion is).
- Pick up Kings. For me, it adds 750 hp unbuffed. That's more than untalented PW: Fortitude does. And with Fortitude or Blood Pact on you, it adds even more.
- Imp HoJ is really optional. It can be nice to aggro 2 mobs at the start of the fight before your first GCD kicks in. It can help in 5 mans, but the situations where it would be off CD while it would be on CD without the talent are rare.
- Reckoning is really nice for single mob aggro. Whenever it triggers, you basically get 4 additional swings with 4 additional SoR/SoV/SoB charges as well. It's also nice when you're grinding.
- 1H Spec is rather useless atm, but this is getting quite a boost next patch, as it raises all your damage by 5%, as long as you wield a onehanded weapon, including spells like Consecration and Avenger's Shield.
- Ardent Defender is nice for grinding and regular 5 mans, but in Heroics/Raids, by the time it can activate you will still be oneshotted despite the damage taken.
- If you're serious about tanking (and want to go Heroics/Raids), getting both Anticipation and Deflection up to 5/5 is pretty much a musthave.
- Even if you go Holy with tanking in mind, pass on Divine Strength. It's completely useless. Instead, take Imp LoH, as it raises both the frequency and effectiveness of your Oh **** button.