Haste, dots and mana return

Time for a little bit of napkin theorycrafting regarding the changes on the PTR for us Shadowpriests with regards to Haste. This can be a bit fuzzy, and the benefits and drawbacks of Haste need to be kept into account, maybe changing what people call the “sweet spots”.

This article is written under a few assumptions:

  • Everyone understands that Haste speeds up casting, not reducing cast time (so at 100% haste your casting time is halved, not negated). With DoTs, this means that at 100% haste a 12-second DoT will run fully in 6 seconds.
  • Shadowform will give the benefits of Haste on Shadow Word:Pain, Devouring Plague and Vampiric Touch (current PTR may have removed SW:P from this list, but no idea if this is intentional or an oversight).

To start with, let’s take a look at the durations with Haste taken into account:

DoT Duration

Nothing special so far, as Haste increases now our DoT durations will shorten. Because the damage done remains the same, our DPS contribution from these DoTs will be increased linearly with our Haste.

To see what this means for your damage, simply check what percentage of your total DPS/Damage is done by each DoT, and then multiply this with 1.X, where X is your haste%.

Example: You have 10% Haste, your DPS by SW:P is 1000, VT is 2000 and DP is 1500. Your new DPS totals for each (after adding Haste) will be 1100, 2200 and 1650. Your new total DPS goes from 4500 to 4950, meaning an upgrade of 450 DPS (or 10% increase). This is easy napkin math, trinket procs and Bloodlust are just one of many things that can screw over this example, but it gives an indication of what to expect.

Now, let’s take a look at the mana costs:

DoT Mana Cost

With the changes in Haste, DPM (Damage per Mana) will not change, as the increase in cost is buffered by the increase in damage done per second. However, because the mana spent over a particular time period increases, our mana pools will drain dry quicker than before. You will not notice this over short fights (where normally you’d have half a mana bar left) but during long fights (say, Faction Champions) you will get mana starved and need to use Dispersion and Shadowfiend more often.

To combat this occurence, Blizzard has proposed a change to our Glyph of Shadow Word: Pain; with the glyph, our Shadow Word:Pain will give us 1% of our base mana per tick of the spell, yielding the following results:

SWP Glyph

 This means that as Haste increases, we will regain more mana per second from the glyph – which is logical. Haste will also increase the mana cost for our spells, which means we can also make a table with the Mana spent per second assuming our DoTs are continually ticking:


If we take an average of about 25% Haste, we can expect to see an increase in our mana usage of 25% as well – going from 128 MpS to 151 MpS. With the gylph we will regain 15 MpS from our SW:P ticks at 25% Haste.

If we put these to values against each other, we see that we will spend 8 Mana per second more (151-128-15) after patch 3.3 than we do currently. At the extreme of 100% Haste we spend 256 MpS and regain 26 MpS, meaning we spend 132 Mana per second (256-128-26) more.


This is all napkin math, and I think the Live patch 3.3 will not include SW:P as one of our Hasted spells; I think Blizzard wants to have us feel our increased DPS in our Mana Pools.

The DPS increase from Haste will be linear, but as the amount of mana we spend on the spells increases exponentially with Haste, I can expect math buffs at Elitist Jerks or Shadowpriest.com to come up with some interesting models determining at which amount of Haste we get the best DoT bang for the MpS buck.

As always, if you see an error, have an addition or a unique insight let me know, and I will edit my post to reflect this.

Edit: Currently, Shadow Word:Pain has been removed from the wording of Shadowform, meaning it no longer benefits from Haste, only Crit. This means that the mana returns from Shadow Word: Pain are a fixed 1% of base mana per 3 seconds, or 13 Mana per second. This also means our DPS will not go up quite as much as on previous versions of the PTR.

For me personally, this means that with my DoT use (16,7% DP, 16,1% SW:P and 22,4% VT) I will gain about 200 DPS (11% Haste increase over 39,1% of my DPS roughly) instead of about 300 DPS (11% Haste increase over 59,2% of my DPS).

I am not sure why this change was made, most likely the weird mechanics of Crit and Haste procs on SW:P which are then refreshed by Mind Flay, allowing you to pop a destruction potion and a Haste trinket and then roll a High-Crit, High-Haste SW:P throughout the fight…


5 Responses to “Haste, dots and mana return”

  1. Only problem with all the calculations is that fresh update on PTR made SWP not scale with haste. Therefore our mana usage will remain as you calculated but regen from glyph will lower a bit.

  2. Hah, that’s what happens if you open a blog post, write a reply to it and don’t bother to check if there are updates to original post :D

  3. Yes, it’s a bit sad they took it out. If I could wish for one thing it’d be to fix the bug that allows SW:P to maintain non-static buffs when refreshed by Mind Flay, so that it can be safely affected by Haste as well.

  4. I think perhaps they removed the haste benefits to SW:P (even though that was the initial plan) because of the refresh mechanic which, from my understanding, like crit modifiers currently, can be skewed to apply to SW:P indefinitely.

    I don’t think that they intended refreshing SW:P to work exactly like it does atm. And I guess that they don’t like the idea of everyone “cheating” haste boosters at the start of the fight (or race changing to Troll).

  5. Great work, thanks Natarumah. I too really wish they’d fix sw:p or at least fess up to not knowing how. It’s already our weakest dot and if it doesn’t scale with haste will only get worse. I suppose the logic is you don’t need to recast it so it shouldn’t be that powerful, but at least it could work as intended.

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