I could be mistaken, but ritual magic seems almost worthless by the time you hit 4th level spells. I can't think of many spells that have durations or ranges long enough that they can be effectively used if the takes over an hour to cast them. Espesialy when most spells are going to be cast on the round scale. This is exacerbated by the fact that a Mage can cast a memorized spell as often as they want. Skills don't really work as a limit, they'll either be able to cast reliably (or make themselves cast reliably a-la truenaming) or the class wont be worth while since they can't function as they're intended.