These kinds of graphs don't translate well into MOBAs because the team size (5), character count (100+) and drafting mode (ban/pick/ban/pick) tend to create very stale metagames if the game is not rebalanced from time to time. That said, both Riot and Valve have made some pretty crazy balance decisions in the last 12 months.
That post will hopefully come soon. Thanksgiving makes it a little difficult to get out quickly as I'd like.
We haven't seen a MOBA go without patches long enough to test if your theory is correct. Defense of the Ancients ended up at version 6.85 before develop ceased. League gets biweekly patches. DotA2 get monthly patches.
The time scale we are talking about is 5-10 years of fixed metagame development. Which in nearly all games where this happened (primarily fighters and board games) we do continue to see metagame development as long as the game is played competitively.
To assume one subgenre is excluded form this ignores the present data, and makes an assumption that the game is incredibly shallow.
The thing with Dota 2 and other Dota clones is that the depth (problem space) is way too big. There's no way competitive teams would have the time to explore all the combinations and still be successful in a reasonable time frame, with the same roster.
That's why every 3-6 months Icefrog (the main developer behind Dota/the game design lead for Dota 2) makes game balance changes: slight nerfs on the most popular heroes and generally slightly higher buffs on the least popular heroes. The main intent is to break this natural tendency of humans to "cluster".
The bi-monthy(ish) patch cycle prevents this, and just leads to players chasing patch notes.
But I agree with you. The current patch system prevent this from happening. This is why we see such diverse play styles in games like chess, go, and older 1v1 fighters. Since the stagnant nature forces experimentation.
Look how long it took for some of the characters presented in this game to surface (6-8 years for some)- that cycle could literally take decades for some heroes in Dota & co. I actually like patches as a forcing function in this case.
Your examples are actually great at proving my point: it took decades if not centuries for the current varied chess and go strategies to emerge. By that point we won't care about Dota & co anymore, we'll all be in the Matrix :)
If your theory is correct highly complex games like Chess, Dota, and Go this shouldn't possible. Yet we've seen it happen.
All that has to take place is clustering, not optimal clustering just clustering.
We're also probably attacking the problem from different angles - I'm mostly thinking about completely disregarded strats/characters.
For example in Dota push strategies (where you try to overwhelm your opponents very early in the game, a sort of all-in strategy) were valid during a very short period, one of about 6-9 months in 2008, IIRC. Then they were basically impossible until 2012.
Also some heroes have been constantly bottom tier ever since competitive Dota started in ~2006 (Spirit Breaker - I'm looking at you!).
It's much more easier to experiment as a single player. Once you get more people involved, social dynamics start happening. And there's nothing harder to budge than social inertia, IMO.
Balance patches in dota happen infrequently, about once every 6 months. And players aren't just chasing patch notes for most of the time.