I remember in the days of 2nd Ed we would ask the DM what level we were going to be and they might say 7th level. This actually meant 7th lvl magic user, as taht was the most expensive chart. Meant you had like a 9th lvl Thief, but it felt even.
IMO, seperate charts for different classes just encourages classes to not be evenly built b/c they can always just balance it out in XP costs. See RIFTS and anything else by Palaldium. See 1st Ed AD&D. No way in heck was the Barbarian an equal class with say Fighter. Things might not be perfect in 3 and 3.5, but at least its better balanced on a class by class basis.
Hagen