I think that it doesn't matter that being able to blind a slime technically makes sense because of soul magic. The point is that it doesn't feel right. The flying creatures are exciting precisely because they are flying, if it doesn't effect the game then it's not exciting anymore. I mean sure, it might suck for some classes to not be able to use some abilities, but getting through situations like that is what makes combat fun. The drakes shouldn't be slipping on the floor not because it's unrealistic but because it strips them of their individuality.