Ok, thus, about legendary cloak :
http://i.imgur.com/vKcvUHm.jpg
On the left hand side, I was at 10% mana when it procced, right hand side 93% and I always clicked off my int procs (jade spirit/trinkets). You can see that mastery does NOT change the damage from the proc, even if tooltip changes...
Edit : Just to be clear, int procs work and increase damage, mastery does not, I think it's bugged since tooltip says it should, as yesterday I tested with/without Mage armor and it was always doing the same damage.