I would like to see the various opinions on the subject of blizzard "balancing" the game around skills that become too powerful in pvp yet are just fine in pve? I have seen them do this for quite some time and am frustrated by this to no end, why penalize a fun or sometimes op ability in pve because it is far too powerful in the pvp environment?
If the OP ability that was toggled off was a key part of your rotation, then going from pve to pvp would cause you to become much less proficient with your class.
If the ability was very powerful and you found yourself relying on that ability in pve, then when moving to pvp you could be surprised or annoyed by it's absence; more casual players may not even know why it's missing.