I have nothing against unpredictable bosses, but only as long as you can, in theory, defend against anything it throws at you. With Meteor, there is a good chance that it will wipe you out and there's literally nothing, and I mean nothing, you can do about it.

Of course Meteor is not a guaranteed insta-kill. But there's a possibility that it is, just like how it is a possibility that he uses it in the first place. When it does happen, it's really just the game telling you, "I've just arbitrarily decided that the fight up until now is zero and zilch. Reset and try again, even though you did nothing at all wrong." Wonderful feature, isn't it?