User blog comment:LivesByProxy/Mastery Redux & Game Design Theory/@comment-5035765-20160120041911/@comment-1330314-20160120064710

Runes already cover the whole stat niche, so if your champion absolutely can't survive without that extra 2 starting armor, you have more than enough options that don't require putting points into masteries for raw stats.

Also, we've had picks like Vel'Koz and Brand, the latter of whom has less CC, as strong supports, so there's little sense in browbeating new ideas just because they seem a little too out there. If Shaco Support can rise in a mastery system that encourages choice and interesting gameplay, then that's just one more advantage.