Spriests aren't using SWD and MF is the spell that deals the majority of our damage so im pretty pleased with the bonus.

Um..you mean Holy Priests aren't casting PW:S on themselves whenever possible?

Do your Holy Priests perhaps die alot?

Whether on themselves or a Tank, Holy Priests have just as much an opportunity to cast PW:S as Disc Priests...the bubble just isn't as nice.

@turn

No, holy priests shouldn't die that often and PW:S shouldn't help that often. When raiding, the majority of the damage should always be aimed at the main tank and off tanks.

PW:S won't help worth much either. At the moment, wearing mostly 25-man naxx gear and valorous in every slot except helm(sigh), I have around 19.5k health. If something hits me and hits me for as much as 22k such as PW:S actually saves me, I'd be impresssed since most trash mobs in 25-man naxx deal between 4k to 7k dmg to me, 9-11k crit.

The boss mobs when they hit a priest such as raveious in the odd time that mc drops from both preists despite having hit cap via hit-gear for that fight and rajuveious? spelling? goes mad, he hits for around 30k and crits for around 45k. Power world shield won't make a difference whether I survive or not. Casting it more or less often in this situation unfortuantely won't save me.

Realistically, its better mana wise for the priest to take the 1-2 hits from the trash mobs till the ot/mt pulls him off you in vent as you've notified him and just do a self-cast lighter heal which if it crits does 8k healing for 500ish mana rather than 2.5k shield for 800 mana.

Personally, I'd prefer something like the Paladin's set bonus. Increased frequency of a 6 second buff giving +50% chance to critical on healing spell? I'd love to have a buff that gave me +50% chance to critical with light heals. Especially considering talented right, you could easily get 1-3 free instance casts within that period and possibly a free light/greater heal as long as it is casted within 8 seconds.

Why do you think spellpower isn't going to come into play for you as a discipline priest? It seems far more useful to disc priests to me, they'll be casting shields anyway and they don't have all the spellpower boosting talents that holy priests have (so it's less likely just to cause even more overhealing).

I use SW:D to proc spirit tap if it's not up.

It's the five second duration after casting the shield. Disc priests won't be taking full benefit from it, because the shield combined with the tank's avoidance means that they usually aren't taking big hits in the short time after a shield is cast on them.

As far as a shadow priest not using SW:Death, if you're not using that as a regular part of your rotation, you're losing a lot of DPS there. Bad choice.

I see a noticable difference when I don't use SW:Death in my rotation compared to when I don't. Also comparing it to other spriests in my raid group who don't use it every time it is up, my DPS is higher.

SW:D is a DPS loss. Anecdotal evidence of "I use it and I do more DPS than that other guy" doesn't prove anything. Go read shadowpriest.com or elitist jerks before continuing to spread ignorant misinformation.

The 4-piece bonus is great for Discipline. In that small window of time, a discipline priest can fit in a couple big heals easily with Borrowed Time for some great burst HPS. Also, it's realistic to think that Discipline could keep the buff going throughout a fight.
For holy, it's not useless, but no (good) holy priest is going to be continually throwing around their baby, mana inefficient shields to try to keep the buff rolling.