Why, though? What do you gain by making all the advancements happen at the same level for every class, apart from consistency?everything should have been:
1-3-6-10-14
Sometimes it makes more sense with the class fantasy to have things kick in at different levels: some classes have it baked in from the start (sorcerer needs to know their bloodline), while others can start out as generalists and specialize later (wizard, fighter).
Personally, I'll take flavor over consistency, given the choice.