User blog comment:LivesByProxy/Mastery Redux & Game Design Theory/@comment-24333627-20160121000257/@comment-26815373-20160121051619

I'll admit I may have overshot or undershot some of the numbers. I did intend for these masteries to have power below that of the Keystones but higher than what we've seen from past, lower tier masteries. Also, as Will mentions, it would behoove me to think of some way to make each mastery here have some kind of immediate visual feedback in-game, so as not to be  examples of huge invisible power like you and Iffem say (rightly) that they are. I'm still working on it.

The real important thing (what I was aiming for) was to have masteries that actually encourage mastery of the game's mechanics - last hitting, landing your skillshots, taking towers, warding, focusing, kiting, peeling, juking, etc. Emphasizing 'best practices' within the game by using an out-of-game power / reward system as a subtle goad. :3