It's not about difficulty. In fact, unnecessary overtuned content is what killed WoW for me (among many other things). So the last thing I want to see in vanilla/tbc legacy servers is multiple difficulties again.
Well, that's how it's done on all private servers and I personally have no issues with it. I remember, for example, back in very early TBC hunters still had that shitty huge minimum range and no Aspect of Viper. I do NOT want to play that part of TBC again.