The newly added (patch 10.2) PvP Talent Jinx, is making Curses cost 3% mana per cast instead of 1%. Since Warlocks only passively regen 1% mana per second this leads to situations where you can deplete your mana very easily (especially with high haste) without ever pressing the buttons designed to deplete your mana (Drain Life, Fear).
Surely this is an oversight, right? The talent already “punishes” you by making your Curses cost soul shards. I’d argue that Jinx should make your Curses cost ZERO mana. Or at the very least, it should only cost 1% mana for the Curse itself and the Agony and Corruption should be “free”.
Additionally (if a dev happens to read this) there are multiple other mana issues that Affliction has that I detail in the thread I’ve linked below.
The big one is that when stacking a lot of haste, Drain Soul’s rate of mana consumption greatly outpaces the passive 1% mana regen.
However besides these two issues I believe that Warlocks (and any other mana using dps, minus Arcane) should be updated to match how Balance Druid is designed right now. Nothing should cost mana except spammable heals, cc, dispels, spellsteal, etc. If balancing is a concern then simply increase the mana costs of these spells to match whatever number of times per minute you believe we should be able to press these abilities.
This change fixes the problem of being unable to press the majority of your buttons (in Warlock’s case) when completely out of mana.