An apparent last-minute bug which was not found on the PTR before the patch was finalized has caused the client and server to disagree on the way haste affects resource generation. This bug will manifest itself in the UI showing a player they have enough resources to use an ability, but the server correctly prevents it as they in fact do not. A death knight for example might see a rune light up that isn?t actually available so when they use the ability, it won?t fire. A rogue may think they have enough energy to use Sinister Strike, but they can?t actually afford it so when they push the button, they will get an error. This bug could affect rogues, death knights, hunters and Feral druids, because these characters all gain more resources from haste. It will also affect buffs that affect attack speed, such as Slice and Dice, Windfury, Icy Talons, and Hunting Party, but also attack speed lowering effects like Thunder Clap. We're currently working on a fix.