Outside of combat, players are just using it for convenience and not for any kind of combat benefit. In this sense it is a buff not a nerf, but either way players can still use /cancelaura for their own personal macros – they just have to hit the button. Shifting between AoE and single-target healing at the push of a button is very convenient.
Holy priests could also have both bonuses as passive effects since there's no real commitment. The single-target or AoE healing provides a meaningful choice that you can use the knowledge of an encounter and coordinate with other players, as well as draw upon your experience and gut instinct as a priest. At the same time, it's not a permanent commitment the way choosing between Disc and Holy is locked in during combat. If you picked the wrong Chakra, or the situation changes, you don’t need to wait too long for a shift. It is impossible to use AoE spells during the single-target mode.