They had this for a long long time but then some time back they divided the skillset into PvP and PvE. It meant that any balancing done for PvP would only be reflected in a PvP area and in PvE areas they behaved like normal PvE skills. This allowed them to tweak skillsets as and when then liked for the differing environments. It was one of things people complained a lot about and although they did not have to do it they went ahead and implemented it.

Guild Wars is a PvP game, so naturally most of the the updates will be for PvP, shocking, I know. PvE also doesn't need balance nearly as much as PvP does; as long as there isn't anything that's impossible to complete or a skill/skill combo that's incredibly broken, like Ursan Blessing, PvE can be left alone. The Visions of Regret nerf wasn't all that necessary, but Cry of Pain had a nerf coming since it was created. Hopefully Arenanet will get around to nerfing some more commonly abused PvE skills in the future (cough, Save Yourselves!, cough).