Combat resurrections are an extremely powerful tool that players have while in combat. Naturally, we apply some limitations. In Mists of Pandaria, that limit was 1 resurrection during a given raid boss encounter for 10-player modes and 3 for 25-player modes. With Flexible difficulty introduced in Patch 5.4, we erred on the forgiving side, and gave Flexible Raids 3 resurrections regardless of raid size.
In Warlords of Draenor, the Flex tech has expanded to more difficulty levels, and we needed a new system to handle combat resurrections more fairly. We knew that continuing with a constant 3 would encourage using the smallest possible raid sizes, while scaling with hard breakpoints would discourage specific group sizes just under those points. Additionally, the limit is not shown anywhere in-game, so it can be easy to lose track of how many resurrections the raid has available (or even know that the limit exists).
So we've built a new system to be more transparent, and improve usability.
During a boss encounter, all combat resurrection spells now share a single raid-wide pool of charges that's visible on the action bar button.
Upon engaging a boss, all combat resurrection spells will have their cooldowns reset and begin with 1 charge. Charges will accumulate at a rate of 1 per (90/RaidSize) minutes.
A charge will only be deducted when a combat resurrection is successful (when the target accepts the resurrection).
Raid frames now show a debuff indicating that a dead player has a pending combat resurrection available.
Outside of raid boss encounters, combat resurrection spells retain their normal cooldown behavior.