It's not even a matter of whether or not SOTA is good, it's a matter of "Are all of the other keystones any good?" The answer to that question is no. The only champions I ever see taking a different Keystone besides SOTA are Kha'zix and Lee Sin, and that's only because they would rather have the ability to invade the other jungler or get off a gank that will actually result in a kill.
SOTA scales extremely poorly as a keystone, it only gives 300 health in total, (which is nothing considering giant's belt gives more health without having to wait 15 minutes or so for it) and the heal on it is so conditional it's sad. Better hope there's a cannon minion dying nearby for that clutch heal in the middle of a teamfight, bro.
I can tell you right now, if ANY of the other offensive keystone masteries affected the jungle camps (Grasp especially for tanks), Strength of the Ages wouldn't even be a Keystone anymore, nobody would have a reason to use it. And that's fucking sad considering the Keystones were supposed to be a way to supplement different play styles by giving you a variety to choose from. SOTA needs to be looked at and possibly reconfigured. Warlord's Bloodlust has been reworked, and it's going to need another one soon considering how few people actually use it. It's about time SOTA got turned into something more interesting as well