Personally I think Blizzard should just have the classic concept of:
Bigger time = Bigger reward
So dungeons like Old Hilsbrad etc, the really long ones — To give bonus exp, higher gear drops and maybe edit the follow NPCs to walk / run faster & put some fun rare drops in (pets, mounts or toys).
That way instead of just removing something that others may enjoy — You make it better for more people to enjoy. Providing greater rewards for the struggle & time poured in. 