I don't understand the celerity changes at all

Sorcery has been since day one of runes reforged really underadvantaged and barely had the amount of usefullness for mages that other champ classes like assassins and marksmens could get from Precision and Domination. Now those celerity changes just makes Sorcery take another step from "Empowered abilities and resource manipulation" to "A mobility focused tree who happens to have one or two things that are usefull for its main users, immobile mages". Seriously, Sorcery is just looking more and more like Domination 2.0