On phone so won't go into much detail atm. Careful what you wish for -
Having abilities unaffected by buffs means they're unaffected by debuffs, too, both healing done and healing received ones. These have existed in the past and may exist in fights in the future, and I don't just mean Ramuh. Might call em fringe cases, but they exist. And can be used while silenced, just to throw that out there. While generally it'd be a boon to let these things be affected, especially with defiance, it's worth keeping this in mind.
This was a specific, intended change back in HW, as asylum was initially buffed by divine seal at launch, leaving us unsure what the developers wanted. When they patched it to be unaffected like other healing abilities and mentioned it in the patch notes, the intent was clear.
We have more and more ability heals, and I see SCH specifically sometimes passing on largesse. Perhaps they will reevaluate it at some point, but currently it is very much intentional. I know it feels odd with warrior and defiance, believe me. I always felt they should benefit from defiance's increase across the board, but here we are.