The 'hardcore' get the mounts & titles during the expansion.
The 'casuals' look at think oh thats cool I'd love that mount and/or title.
New expansion rolls around the hardcore demand that all the titles and mounts are removed so that no-one they deem casual can infringe upon them feeling special. And the sequence will repeat itself at the end of every tier and every expansion. I honestly don't give a damn if someone goes back to wrath content and gets a title I have or a mount I have. It's a game and some people will really want a particular mount because its really cool to them and they want to go back and get it when its possible for them to. I think that the yogg0 mount, LK mount should just remain 100% 1 drop per kill if its important to people they'll go get it, if its not they won't. The 'hardcore' guys will be showing off their brand new epeen mounts so fairs fair really. Putting it to a rare drop just screws over anyone not in a high-end raiding guild and guarantees that next to no-one will every visit the old raid content.
Hell I'd be fine with them making my realm first title possible to obtain if people go back to the old content for that stuff.