Regarding Shield Block versus Shield Barrier (and mastery), GC said this today:
I was boss today on Lei Shei testing because all of her damage was magical, so I was popping muh Shield Barrier on every other cast almost and mitigating a lot of damage.
I'm really glad our barrier is looking at strong as it does. I believe you made mention of it yourself freese but to reiterate, I think a big missing piece to warriors was the lack of a pure magical DR ability.
How much of a benefit do you feel de linking LS and RC will have? Also, do you see VR being included in our rotation more often than what it was. I never put points in Impending victory but i i have always felt it was an ability(un-spec'ed Victory rush) that showed potential.
I am going to answer some stuff that you asked here, and I hope it will start some more discussions.
I have found that "the best" with regards to Shield Barrier and Shield Block completely depends on the situation. This may be frustrating for some people, but I forsee a lot of MoP tanks having to adapt and react to whatever the situation calls for. This is (mostly) far removed from Cata where we could give general advice like "use this spec for everything" or "gem this specific way for everything." In many of the MoP raid bosses I've tested so far, I could be using Shield Block 9 times in a row but then switch to Shield Barrier for one special attack.
On the Sha of Fear test, for instance, I used Shield Block while tanking the boss himself because he hits hard. In situations where the boss is consistently hitting hard, Shield Block will be good because you get more long term survivability. Then, when I was transferred to a different platform on this fight, I used nothing but Shield Barrier because there were these orbs that have to be collected or else they will heal the mob you're trying to kill. These orbs do magic damage to the player and restore the player's primary resource (i.e. you run over the orb and it automatically gives you 100 rage). The latter mechanic allowed me to spam Shield Barrier and collect a majority of the orbs so that the DPS could focus more on killing the mob and the healer could focus on healing.
With regards to unlinking RC and LS: this was a welcome change. Also, I am very glad that I no longer have to save my shield wall for the raid. The problem with prot warriors in Dragon Soul (at least before all the major nerfs) was that we had to save our personal CDs for the raid. This meant that we took more damage than other tanks simply because we couldn't use our personal CDs for ourselves. During Heroic Yorsahj progress (again, before the nerfs), I died many times because I had to save my shield wall for the heavy AoE damage combos. On the one hand I like being able to supply the raid with some sort of damage reduction CD (like the Demoralizing Banner), but I don't want to have to sacrifice my own surviability to do so.
I see that some people are talking about the differences between Victory Rush and Enraged Regeneration. Personally, I've been running with glyphed Victory Rush on all fights simply because it has a shorter CD. The key to using VR (and ER for that matter) is to time them correctly. For instance, if you were anticipating a big attack, you could use your VR and Healthstone right after the hit occurred to heal yourself for a substantial amount of damage. I suck at math myself, so I'll wait to see what those who are better with calculators have to say about the two; again, I've just been running with VR because I like it better.