NOTE: Since my original posting, Blizzard has changed Vampiric Touch to restore 3% mana every time it does damage (18% mana returned per cast, assuming no clipping on refresh). This should largely fix our mana problems, especially in multi-DoT situations. The points raised in this post are still valid but should be seen from the perspective of mana costs for abilities and why Vampiric Touch is our go-to for mana regen now.
As I have mentioned previously, mana regen is a huge problem in the Mists of Pandaria beta test for Shadow Priests. Before I dive in to the math, allow me to list out the current sources of mana regeneration and the costs of all spells associated.
| Mana Regenerators | |
|---|---|
| Dispersion | 6% every 1 second for 6 seconds = 36% = 36k @ 85, 72k @ 90; 2 minute CD = 1500mp5 @ 85, 3000mp5 @ 90 (average) |
| Shadowfiend | 3% per attack for 15sec, 10 attacks total = 30% = 30k @ 85, 60k @ 90; 4min CD = 1250mp5 @ 85, 2500mp5 @ 90 (average) worst case; 2min CD with losts of Mind Flay casts = 2500mp5 @ 85, 5000mp5 @ 90 (average) best case |
| Hymn of Hope | 2% every 2 seconds for 8 seconds = 8% = 8k @ 85, 16k @ 90; 6 minute CD = 111mp5 @ 85, 222mp5 @ 90 (average) |
| Base in-combat regen | 1.25% every 5 seconds (average) = 1250 mp5 @ 85, 2500mp5 @ 90 |
Core Spells
| Spell | Mana Cost (%) | Mana Cost (@ 90) |
|---|---|---|
| Mind Blast | 3% | 6000 |
| Mind Flay | 1% | 2000 |
| Mind Sear | 6% | 12000 |
| Mind Spike | 3% | 6000 |
| Shadow Word: Death | 2.6% | 5200 |
| Shadow Word: Pain | 4.4% | 8800 |
| Shadowy Apparition | 0% | 0 |
| Vampiric Touch | 3% | 6000 |
Situational
| Spell | Mana Cost (%) | Mana Cost (@ 90) |
|---|---|---|
| Dispel Magic | 2.6% | 5200 |
| Fade | 3.5% | 7000 |
| Fear Ward | 0.9% | 1800 |
| Leap of Faith | 2.6% | 5200 |
| Levitate | 0.9% | 1800 |
| Mass Dispel | 38% | 76000 |
| Mind Vision | 1% | 2000 |
| Power Word: Fortitude | 4.4% | 8800 |
| Power Word: Shield | 6.2% | 12400 |
| Psychic Horror | 0% | 0 |
| Psychic Scream | 3% | 6000 |
| Shackle Undead | 9% | 18000 |
| Silence | 0.9% | 1800 |
Talented/Spec’d
| Spell | Mana Cost (%) | Mana Cost (@ 90) | Notes |
|---|---|---|---|
| T1 / Level 15 | |||
| Void Tendrills | 4% | 8000 | |
| Psyfiend | 4% | 8000 | |
| Dominate Mind | 2% | 4000 | |
| T2 / Level 30 | None | ||
| T3 / Level 45 | None with mana cost | ||
| T4 / Level 60 | None with mana cost | ||
| T5 / Level 75 | |||
| Power Infusion | 6% | 1800 | Reduces mana cost by 20% for 15sec |
| T6 / Level 90 | |||
| Cascade | 14% | 28000 | |
| Divine Star | 7% | 14000 | |
| Halo | 28% | 56000 | |
So what does this all mean? The table below outlines the amount of time it would take to go from 0% mana (@ 90) to 100% under various circumstances. NOTE: I did not include Hymn of Hope in the following table because it does not decrease any of the combination times except for moving Just in-combat regen to 366sec (2 casts of Hymn of Hope).
| Condition | Rate | Time (sec) | Notes |
|---|---|---|---|
| Just in-combat regen | 2500mp5 | 400sec | |
| In-combat and Shadowfiend (worst case) | 3125mp5 | 320sec | Two Shadowfiend casts total: Cast one = 0sec (13.75% @ 15sec) Cast Two = 240sec (83.75% @ 255sec) |
| In-combat and Shadowfiend (best case) | 3571mp5 | 280sec | Three Shadowfiend casts total: Cast one = 0sec (13.75% @ 15sec) Cast Two = 120sec (53.75% @ 135sec) Cast Three = 240sec (93.75% @ 255sec) |
| In-combat and Dispersion | 7937mp5 | 126sec | Two Dispersion casts total: Cast one = 0sec (37.5% @ 6sec) Cast Two = 120sec (100% @ 126sec) |
| In-combat, Dispersion, and Shadowfiend (either case) | 8065mp5 | 124sec | Two Dispersion casts and One Shadowfiend cast total: Dispersion cast one = 0sec (41.5% @ 6sec) Shadowfiend cast one = 0sec (46% @ 15sec) Dispersion cast two = 120sec (100% @ 124sec) |
Something very important to keep in mind that this is how long it would take you to go from 0% mana to 100% mana while in combat [u]and while not casting any other spells[/u]! If you run OOM on a boss fight (and believe me, you will), here is a rundown of how long it will take you to be able to cast each spell given that your Dispersion, Shadow Fiend, and Hymn of Hope are all on cooldown:
| Spell | Mana Cost (@ 90) | Time Before Cast |
|---|---|---|
| Core Spells | ||
| Mind Blast | 6000 | 12sec |
| Mind Flay | 2000 | 4sec |
| Mind Sear | 12000 | 24sec |
| Mind Spike | 6000 | 12sec |
| Shadow Word: Death | 5200 | 10.4sec |
| Shadow Word: Pain | 8800 | 17.6sec |
| Shadowy Apparition | 0 | 0sec |
| Vampiric Touch | 6000 | 12sec |
| Situational | ||
| Dispel Magic | 5200 | 10.4sec |
| Fade | 7000 | 14sec |
| Fear Ward | 1800 | 3.6sec |
| Leap of Faith | 5200 | 10.4sec |
| Levitate | 1800 | 3.6sec |
| Mass Dispel | 76000 | 152sec |
| Mind Vision | 2000 | 4sec |
| Power Word: Fortitude | 8800 | 17.6sec |
| Power Word: Shield | 12400 | 24.8sec |
| Psychic Horror | 0 | 0sec |
| Psychic Scream | 6000 | 12sec |
| Shackle Undead | 18000 | 36sec |
| Silence | 1800 | 3.6sec |
| Talented / Spec’d | ||
| Void Tendrills | 8000 | 16sec |
| Psyfiend | 8000 | 16sec |
| Dominate Mind | 4000 | 8sec |
| Power Infusion | 12000 | 24sec |
| Cascade | 28000 | 56sec |
| Divine Star | 14000 | 28sec |
| Halo | 56000 | 112sec |
It should be noted, however, that if you have Power Infusion as a talent, it will reduce the mana cost of spells by 20% for 15 seconds. The following table assumes that you have Power Infusion cast upon yourself. NOTE: Think of this table as “this is how long I would need to wait in order to cast one of these spells if I also had enough mana for Power Infusion on top of it.” This is NOT how you would use this spell in a real situation, rather you would want to cast this spell at the beginning of a fight or after you have used Dispersion to increase your longevity on the mana you have.
| Spell | Mana Cost (@ 90) | Time Before Cast |
|---|---|---|
| Core Spells | ||
| Mind Blast | 4800 | 9.6sec |
| Mind Flay | 1600 | 3.2sec |
| Mind Sear | 9600 | 19.2sec |
| Mind Spike | 4800 | 9.6sec |
| Shadow Word: Death | 4160 | 8.32sec |
| Shadow Word: Pain | 7040 | 17.6sec |
| Shadowy Apparition | 0 | 0sec |
| Vampiric Touch | 4800 | 9.6sec |
| Situational | ||
| Dispel Magic | 4160 | 8.32sec |
| Fade | 5600 | 11.2sec |
| Fear Ward | 1440 | 2.88sec |
| Leap of Faith | 4160 | 8.32sec |
| Levitate | 1440 | 2.88sec |
| Mass Dispel | 60800 | 121.6sec |
| Mind Vision | 1600 | 3.2sec |
| Power Word: Fortitude | 7040 | 14.08sec |
| Power Word: Shield | 9920 | 19.84sec |
| Psychic Horror | 0 | 0sec |
| Psychic Scream | 4800 | 9.6sec |
| Shackle Undead | 14400 | 28.8sec |
| Silence | 1440 | 2.88sec |
| Talented / Spec’d | ||
| Void Tendrills | 6400 | 12.8sec |
| Psyfiend | 6400 | 12.8sec |
| Dominate Mind | 3200 | 6.4sec |
| Power Infusion | 9600 | 19.2sec |
| Cascade | 22400 | 44.8sec |
| Divine Star | 11200 | 22.4sec |
| Halo | 44800 | 89.6ec |
As you can see, when you run out of mana and don’t have a cooldown available, you’re dead in the water and not contributing at all to your party’s DPS. This happens. A LOT. At this point it appears that for longevity reasons, it may be a better idea to take Power Infusion over Divine Insight for your Tier 6 / Level 75 talent (NOTE: DI is bugged at the moment and ALWAYS procs on a Mind Blast hit, causing the number of SW: Death casts to rise, which is also contributing towards going OOM).
This is something that Blizzard [b]has to[/b], otherwise Shadow as a raiding spec is infeasible even under the best of conditions.