Fundamental Problem with Keystone Masteries
Let me say first that, although I enjoyed the old mastery system because it was a subtle point of optimization, I really appreciate what Riot is trying to do with the new system. I think creating "meaningful choices" (to borrow a phrase peppered into all the patch notes) is a good thing to do. However, I don't think the keystone mastery system accomplishes this.
Before keystones, the only way to change the way your champion played was with items (and, to a small degree, runes and summoners--but runes were very generalized and summoner spells have infrequent impact due to high cds). This is a fantastic strategic element to the game because it gives designers a lot of levers to pull and players a lot of meaningful choices to make. Some items have such powerful synergy with the kits of some champions that those items become "core," and are generally more valuable to buy than anything else. However, you can greatly customize your build based on the advantages and disadvantages of your team, and continue to do so as the landscape of the match changes.
Keystones, on the other hand, are selected once you can see enemy champions but before you can see their summoners, their keystones, their runes, etc. They are then set in key-stone (in b4 9k+1 downvotes and 1 upvote from Phreak) for the rest of the match. You made your decision at a point when the only information available to you was the champions being played and limited information about how your team plans to build. At this point, far and above the most important component of this decision is what kind of synergy your champion has with the keystones. That means that most of the time there's going to be one optimal choice and a bunch of non-optimal choices. This is not the kind of "meaningful choices" Riot is seeking to create, and results in "noob traps," which Riot continues works to remove.
The problem with new masteries isn't that there are 8-10 Thunderlord's Decrees in every game (although it's popular and easy to point out). This just means Thunderlord's is better than everything else, and that means there's no "meaningful choice" to be made--Thunderlord's will almost always be the "right" choice.
The problem with new masteries is that, for most champions, there's always going to be one mastery setup that will be optimal, or at least has the best chance of being optimal with the information you're provided in champ select. By making keystone masteries that occur frequently in-game and have actual impact, champion synergy is unavoidable, and the keystones are so disparate that one is usually just plain better than the others. Soraka will always take the healing keystone. There's no meaningful choice there--just a buff to soraka (that I doubt too many people were thrilled about).
If the purpose of redoing masteries and establishing keystones was to make another layer of optimization with its own complexities and pitfalls, then it has succeeded. And that's fine. I personally don't think it was necessary, but I don't think the game is any worse for having it, so long as they can be correctly balanced (which is a big if, considering how many levers Riot pushed, pulled, and added in preseason). To quote the "Fundamental Philosophy" on masteries from the patch 5.22 notes:
>We're updating the mastery system to offer focused, high-impact choices rather than a slew of nuanced micro-math optimizations. Each tier of decisions now successively grows in importance, ending in your final 'keystone mastery' which fundamentally impacts how you play your champion.
While the choices are (mostly) higher-impact than old masteries, I don't think that adding a "fundamental twist" on how you play your champion inherently adds value to the system when there's almost always going to be a clearly optimal choice, and there will always be one so long as the masteries are high-impact. That's a real catch-22.
