Checking the first few pages of raider io here and there (the “Timed Runs Leaderboards” specifically), I notice the high-end Prot Pallies are using Blessed Hammer instead of Holy Shield??
Am I missing something? I would imagine a minor 12% damage reduction from 1 auto attack doesn’t make much of a difference, especially with how hard some of these trash mobs can hit.
Or is this talent being taken just to “fish” for more Avenger Shield resets (since Blessed Hammer is usable even out of combat)?
Blessed hammer does more damage in aoe packs and you can use it to hold aggro while you kite mobs.
This, and it allows shield procs while kiting as well for more damage/interrupts.
That said, top pallies are in coordinated groups and play together a lot. Having synergy with your group is incredibly important for timing higher keys. A tank/healer combo familiar with each others playstyle is crucial to success.
I run holy shield almost exclusively because I hate blessed hammer and from the pally streams I watch, I pace them on damage. So either is viable.
I hadn’t considered that, but it makes sense 
Because they are grouped with good players, I imagine these high io Prot Pallies take less damage “in general” when you factor in the fact that good players actually help with interrupts, actually use their CC, actually do mechanics properly.
Obviously random PUGs do not do these things (interrupting, using CC, doing mechanics, etc), or they are hit and miss at doing them. Probably why I think Holy Shield is better - for WHEN, not if, those interruptible casts go off and hit me 
In terms of physical mitigation, they actually work out pretty close. In most keys, raw melee hits is by far the biggest source of incoming damage; and a 12% spammable reduction is very significant.
Aside from that, Blessed Hammer can be used for kiting and is wonderful at picking up spawing adds; while Holy Shield gives very strong magic mitigation. Both completely viable choices, I swap depending on the dungeon. Holy Shield for ML, Shrine, Temple and Waycrest (and KR Fortified solely for Zul), otherwise Blessed Hammer.
When I simmed blessed jammer against holy shield it simmed 3k dps higher. I run it to have more consistent damage intake, block is still rng and can lead to bursty damage spikes. There are a few dungeons where holy shield is better defensively, shrine, last half of motherlode, fort weeks on waycrest.