Heh. I've made level 20 magic users that had no ranks in Spellcraft before, Guns. It depends on what you focus on. (In that case, I was playing a Warlock that could get a Bluff check in the low 100s pre-epic.)
As far as Arcana goes, however, the parallel doesn't fly. Arcana is used for designing new formulas, be they spell, focus, or ally spirit formulas. That's it. Nothing to do with the actual use of the formula. You don't even have to be Awakened to do it. There is absolutely no connection between Arcana and level of magical skill. You can be a very proficient magician using formulas you purchased from others.