In the example of taking out Mono-Aether, it would cost what, 60hp to take out a single elite phase dragon? And though I'm not experienced with the deck, I'm betting aether can whip out more than one of those at a time, or stick in some elite immortals/sparks/lobotomizer or something. So unless you're made of shards and miracles, I really don't think fire buckler is going to help you much... >>
It's effectively paying HP to get rid of immortal creatures, (creature's attack)*(creature's defense), at best.