This thought is prompted by the upcoming change to Blessing of Sacrifice in patch 2.2:
Blessing of Sacrifice now has a 1-minute cooldown.
It's pretty much aimed at PvP, where Sacrifice is constantly used to break Crowd Control for paladins. However, this change makes Sacrifice useless for both PvP and PvE purposes.
Admittedly, Sacrifice doesn't get used an awful lot in PvE. But there are times when it is useful. I use it on AoE packs to keep multiple mages up. I have fond memories of almost killing myself with it in the BWL Suppression Room. (It turns out that putting Sacrifice on 8 mages/warlocks adds up to a lot of damage.) It's also useful for controlling Greater Blessings, allowing you to put Greater Blessing of Salvation on DPS warriors and "clean" it off the tanks. There are a few fights where you can use it to break Crowd Control (for example, Maiden of Virtue, or Moroes for a paladin tank). I've even used it on the tank, to mitigate damage, if I am on Salvation duty.
It's a neat little spell with a lot of uses. It's not a spell you use all the time, but comes in handy on occasion. However, this cooldown pretty much makes the spell useless for my purposes.
The annoying part is that yes, Sacrifice is probably overpowered in PvP. Virtual immunity to crowd control is overpowered, even if you can purge/dispel it. But adding the cooldown removes it from both PvP and PvE.
Maybe it would be better if Sacrifice was tagged "PvE-only" and you could not use it in Arenas. There are already several spells that are effectively PvE-only: Lay on Hands, Righteous Defense, Taunt, Blessing of Salvation, etc.
There are probably several other spells that could benefit from the same treatment. And maybe Blizzard could introduce PvP-only spells, which could only be used in arenas.
PvP and PvE are very different creatures. Is it really ideal to attempt to balance for both simultaneously?