Point is, this is called "overhealing", when you're healed for more hp than you have and the healer gains the enmity just the same as if you'd actually needed the full cure.

This is why regens on pulls can cause havoc--because the healer gains the full value of the regen and you have no hate on anything but one target until you flash.

This contributes to why white mages generate so much hate on fights like titan. Every tic of every regen and medica2 is giving them the same amount of hate, whether the target gained hp from it or not.