Spectre's passive is how Galio's Bulwark should work.
The current design is ancient, and honestly, poorly thought out, Galio heals off of damn near everything with the bulwark up, especially dots and minion waves. A flat amount of health per damage taken is something that should not exist in this game. I get that he has no play rate, but this should be taken care of because it sucks to play against, and there's no way to keep him from abusing it.
If it works like spectres, it still fucks with dot champs. Not as hard. He can't face tank a minion wave to heal a bunch of health. He does still need a full rework tho