I believe a lot of that is due to visibility, strange as it may sound. I got to see the effects firsthand of League becoming a spectator sport: people improved, a LOT. When competitive games became popular to watch, as Youtubers and streamers got big audiences, players improved. Suddenly, massive numbers of people were seeing these plays and these strategies, and it educated the playerbase. People learned more about the importance of different things, like vision, dragon control, etc.
That's not to say that everyone is a pro. One game of solo queue is all you need to see that's not the case. But, in general, people learned from this surge in visibility. Trickle-down strategy is now the norm, in large part because of this.
It worked a little bit in Dominion, but only because of community effort. There is zero visibility on high-level Dominion play, so there's no trickle-down strategy. If you want to know how the top players play Dominion, it takes quite a bit of effort. You can't just flip on the LCS or one of a thousand streams.
Blizzard is going to cultivate HotS visibility just like Riot did League (specifically SR). With any luck, the same thing can happen, and the objective control will trickle-down.