It no longer becomes a smart heal, they just disappear if they are unused as usual. Although if the Mana Tea change goes through, crit WILL be more valuable as a regen stat.
Mastery vs crit right now. I've been trying to look at other mist weavers and it seems most are reforging straight to crit. Even for 25 man raids. The reason being that in 10 man the spheres don't get used enough because not enough people are moving around to collect them all while in 25 it is the opposite so even reforging OUT of mastery, it can still make up 10%+ of your healing.