Learning when you cannot harm target

Not sure if this is intended but you don't learn anything at all from non-offensive supplications/spells if your fighting someone immune to the weapon's attack.. What I mean is: A groupmate is fighthing a mob. I enter, but don't assist, to heal the groupmate. I get drawn into the fight but mob is immune to my attacks. I'm still only healing the groupmate though, so I don't care if I can't harm the Mob.. But, if I would learn something from the healing supps, I get the message I can't since the Mob is immune to my attacks. Is this how it's intended to work ? I don't see why Benefical Supp/spells communed/cast on ANOTHER wouldn't allow for improvement... But I'll understand if it's "By Design".