This has been reported many times, by many people, both on the forums and in game. Any experienced Affliction Warlock PVP player is painfully aware of the Soul Rot Drain Life mana bug. I decided to test it a bit more to understand exactly what is happening (doing Blizzard’s job for them). I’ve found that there are at least two Soul Rot + Drain Life bugs.
[1] Soul Rot’s tooltip states that Drain Life consumes no mana for 8 seconds (same duration as the dot). With the 2 piece tier bonus, Soul Rot lasts an additional 4 seconds. The tooltip is updated to reflect that both the Soul Rot dot and the zero mana Drain Life duration now last 12 seconds. However this is not the case. In fact, both with and without your 2 piece tier, the free Drain Life period is 10 seconds. Ironically, the only tooltip that is accurate is in PVP with the 2 piece tier bonus (2 piece is nerfed by 50% in pvp so only increases Soul Rot by 2 seconds).
[2] Besides the free Drain Life window not matching either the 8 or 12 second tooltips, this zero mana period has another bug. Drain Life only costs zero mana if the channel can FULLY complete within 10 seconds of casting Soul Rot.
For example with my own haste, Drain Life is a 2.5 second channel. If I cast Drain Life 7.5 seconds after Soul Rot then Drain Life will cost zero mana. However, if I cast it 7.6 seconds after Soul Rot then this Drain Life will IMMEDIATELY start consuming mana even though you are still within the (hidden) 10 second zero mana Drain Life window. This makes no sense. If anything, this Drain Life should cost zero mana for 2.4 seconds and then consume mana for the last 0.1 seconds.
Even if these two bugs were fixed, I think this free Drain Life window is very poorly implemented.
Let’s just pretend that both bugs are now fixed. Now the only real indication of how much longer you can cast free Drain Lifes is by how much longer the dot exists on mobs. You don’t receive any buff to be able to track and Drain Life doesn’t get a proc glow during the free Drain Life window like many abilities do when they are enhanced. The only way to avoid accidentally ooming yourself is by using weak auras to track how long you have left in your free 8, 10, or 12 seconds (again, assuming the bugs were fixed).
It’s extremely clunky and counterintuitive that the free drain life window is hidden. Because you would assume (and it would make sense) that as long as Soul Rot is still active on a target, Drain Life would be free.
I can only assume that the hidden 10 second free drain life window was intentionally chosen to help avoid bug #2 (with no tier, you get a 2 second longer free drain life window than the baseline dot lasts). However if this is the case (being intentional) then the dev(s) failed to take into account extending Soul Rot’s dot duration with Summon Darkglare, Soul Swap, and 4 Piece S3 Tier.
Soul Rot can be extended by 8 seconds with Summon Darkglare, 2-6 seconds (1-3 in pvp) with the 4 piece tier set bonus, and an additional 10 seconds via Soul Swap (depending on when you copy the dot). This means that Soul Rot’s dot can exist for significantly longer than the free Drain Life time lasts. The problem with this is that if you cast Drain Life outside the 8-12 second free period (again pretending bug #2 is fixed) you can nearly INSTANTLY oom yourself depending on how many targets you drain.
Below I’ve listed the mana cost of a single cast of Drain Life for each number of possible targets.
1 = 15% mana (cost of a single Drain Life target)
2 = 30% mana
3 = 45% mana
4 = 60% mana
5 = 75% mana (max initial cast dot targets)
6 = 90% mana (5 dots + drain life non-soul rot target)
7 = 105% mana (5 dots + drain life non-soul rot target + soul swap duplicate 1 dot)
With all my self haste procs / buffs active in pvp (no bloodlust) I can get Drain Life down to a 1.7 second channel. So in less than 1.7 seconds I can deplete my mana from 100% to 0% by pressing 1 button. There is something seriously wrong with this design. This shouldn’t be a thing that can occur.
This is devastating to Affliction in particular (compared to Demonology and Destruction) because Affliction consumes much more mana than the other two specs (especially in pvp). I’ve started two other related threads that I’ll link below. They all relate to the plethora of mana issues that Affliction currently has. Please fix all these bugs and issues.
I propose that this Soul Rot + Drain Life mechanic be simplified by doing exactly this. Drain Life should be FREE as long as you START the channel when there is still an active Soul Rot dot.