Originally Posted by
PapaNasty
It'll be amazingly important, it's a massive buff to damage reduction.
2P essentially means, that at least every 13s (Actually more often, due to procs) your prot paladin will get +50% block chance, for 5s, which should push normal hits off the hit table (Assuming 670+ ilvl gear), and blocks give +30% damage reduction. Once you factor in procs, this will probably end up having a 50% uptime*, or higher.
e.g. If I'm tanking, and didn't take holy shield or have seraphim up, I'd usually avoid or block around 50% of the attacks made against me (Well should lol, RNG can be a bitch sometimes). However, if I had the 2pc bonus, then while it was up (~50% of the time), I'd be blocking all of these attacks instead (so 40% dmg reduction). When you factor in, that it'll only be up 50% of the time, that's essentially 20% less damage over the course of the fight..... which is pretty substantial (Can you imagine if the 2pc set bonus gave a dps +20% increased dmg during a fight? or +20% increased healing to a healer?).
4pc isn't that amazing, it's not controlled by the tank, so you can't choose to use it before a big attack or similar. It might reduce a decent mount of damage, or it might reduce a very small amount of damage. With 1.55 procs per minute, it'll be up reasonably often though, if it has a really high uptime, it'd be awesome, especially when combined with the 2pc bonus and holy shield, but I have no idea what the uptime would be like.
I'd say you should give your prot paladin priority on getting 2pc, and then check back once people have done some testing on the uptime of the 4pc to see how useful it really is.
Also, the 4pc works well with holy shield, but the 2pc doesn't (It actually reduces the effectiveness of holy shield, since block would just get pushed off the hit table).
In general actually, the 2pc will reduce the effectiveness of mastery, as it'll push the extra block % off the table during the 50% uptime, and it'll also encourage prot paladins to stack crit for avoidance, so that they can proc divine crusader for the free avengers shield. Seraphim + the 2pc bonus will be pretty off the charts as far as awesomeness goes, since seraphim will increase our avoidance, so we can proc divine crusader, which should mean we'll be able to ensure the 2pc bonus is up for at least the first 5s after seraphim wears off.
* This is just my own estimate, not based on detailed theorycrafting or similar, but I think 50% should be a conservative estimate of it's uptime (It might have much higher uptime, particularly if refreshing it adds to the time, like what happens with SotR).