Shadow Power, by request
The basic strength and weakness of Shadow Power is the fact it’s purely about the crits. The tooltip first: “Increases the critical strike chance of your Mind Blast and Shadow Word: Death spells by 3/6/9/12/15%.”
Before you add this talent, these two spells each do about 1800 damage per cast (assuming a fairly otherwise standard shadow-talent template). Adding this talent means that 15 times out of 100 you’ll do ~2700 points, for a baseline average of 1935 — a nominal increase of 7.5%.
In a ‘standard’ shadow-weave priority pattern, you will get about a third of your damage from these two crit-eligible spells. As discussed in Crits, this means your 5 talent points increase your total damage by… 2.5%. Except.
Here’s the deal. Crit-oriented casters (like all crit-based players) can be a big deal. To do so, however, they have to emphasize their strength — in this case, their crits.
The first place to look is to realize I’ve “lied” — actually, simplified and so not included — part of your crits. Everyone has a base crit of 4%. Which means your total crit for these two spells is 19%. As casters, you’re inevitably going to add int. At level 70, we get an additional 1% crit for every 80 INT. It’s easy – without really even trying – to get another 6% of crit from int. Which means your probable starting point isn’t 15% or 19%, it’s 25% – which is 12.5% more damage for this pattern.
So before we go to the next stage, we know that as a DPS using a standard shadow spell priority will give us a DPS increase of just over 4%. (at a minimally acceptable 500 dps, we are at 520.) But as I said, there’s another stage.
If you’re going to emphasize crits, you need to emphasize crits. This means your first priority for spells is SW:D and MB (in either order), and you want to minimize the delay between casting them. It’s possible to get up to 50% of your base damage from the crit-eligible spells. Which results in the crits being an additional…
6.25% of your damage. At the aforementioned 500 dps, we’re now up to 531. At a 1000 dps your crits are adding another 62, average. I know this seems small, but it’s actually rather healthy — PROVIDED you did not sacrifice base damage or +hit to get there.
Usually what will be sacrificed, because of the above, is mana regeneration. The Crit specialist is impressive while blasting but is NOT geared for endurance. On the other hand, to avoid stealing aggro the crit specialist will be pausing (or stepping down the intensity) for a while, meaning this is the shadow priest that actually considers dancing the five second waltz. Crit priests are uncommon because this is hard – and counterintuitive – and as the tanks get better the need/opportunity to pause gets less and less common. And… crit priests are uncommon because the gains seem so, well, tiny. They are, however, definite.
To reiterate, Shadow Power is a Crit-emphasis talent. If you’re going to choose it, don’t go half-way or the use will be essentially nothing — and even going all-out the gains will not be earthshattering. But recognize by doing so that many lessons learned and shared amongst the shadowpriest community are not a perfect match for you — you’ll frequently have to learn your own lessons.