I think it's awesome that they found a way to integrate Gandalf's sacrifice moment into the quest (and having it remove the "indestructible" keyword is a seamless way to do that). Defeating a Balrog should entail nothing less than the ultimate sacrifice. As for how this will work out as far as the campaign goes, I guess we'll just have to wait and see.
As a side note, I suppose we have finally found something that Spirit Glorfindel is subpar at... (which is ironic, given his past history)
Maybe it's time for Lore Glorfindel to shine?