I think that holy shield is the superior talent for slaves and overall mitigation. Its amazing for DoTs, trash and constant AoE. It is RNG in nature but I have a ~35% chance on any attack for it to be reduced by block which I think is pretty good. The 10% block chance cant hurt either.

I also just unlocked bulwark of order golden trait and with the extra chance at grand crusader and extra single target damage by avengers shield the first avenger talent I can build shields of 300-500k quite rapidly. I can have strings of good rng where it resets a lot which builds me a little 10-25% hp absorb shield cushion that is fairly easy to maintain and refresh while fighting a boss.

Blessed hammer looks cool and adds some AoE but I think its only the best on that one toon who is taking melee hits from a boss or trash. The other toons will not get any benefit aside from the AoE damage.

I think I'm also going to experiment with Consecrated hammer and see how it plays with bulwark of order and first avenger. Maybe it will be better than holy shield? If it works how I'm guessing it does then each hammer of righteousness it is a spamable 22.5% chance to reset avenger shield each time its used. It also gives us the benefit of consecration without having to be in it, which happens quite a bit if you have to run out of of something or handle a mechanic.

I guess all 3 of the first talents do lose some effect by not actively tanking some more than others.

At least holy shield gives you that +10% block and consecrated hammer gives you the effect of consecration for some of your core abilities and easy pulsing AoE damage without having to game blessed hammer to hit the maximum number of targets. I wouldn't rule out that 20% more powerful light/hand of the protector while running around dodging mechanics. That can be ~7% more total HP healed assuming your light of the protector healed a very low hp target for the full ~30%.

7% HP on a nearly dead DK with hp increasing abilities (vampiric blood) and bone shield can be an extra 200-300k heal or nearly two flash of lights worth of extra healing.