Your healing spells gain a bonus, but it varies with every spell. Casting time is a rule of thumb that doesn't really have anything to do with it.
The bonus gained varies for every spell. Warlocks have charted the % bonus for their spells, and it clearly varies in a way that doesn't really have to do with spell cast time. Hellfire, a 15 second channeled cast, only gains 30%. Shadow bolt, a 3 second cast, only gain 85%, even though its the longest cast shadow spell. Others vary arbitrarily.
Just don't fool yourselves into thinking casting time has any real relevence to +healing or +dmg. It coincides a bit, but doesn't really scale or matter. Each spell gains a individual hard % from +healing or dmg.
The bonus gained varies for every spell. Warlocks have charted the % bonus for their spells, and it clearly varies in a way that doesn't really have to do with spell cast time. Hellfire, a 15 second channeled cast, only gains 30%. Shadow bolt, a 3 second cast, only gain 85%, even though its the longest cast shadow spell. Others vary arbitrarily.
Just don't fool yourselves into thinking casting time has any real relevence to +healing or +dmg. It coincides a bit, but doesn't really scale or matter. Each spell gains a individual hard % from +healing or dmg.