I like how people say the meta is healthy because there are so many viable decks now. But last night I played for 2 hours straight and just saw an endless stream of Secret Paladin, Tempo Mage and Control Priest. Throw in a couple of Zoolocks and Combo Druids for good measure and that is pretty much it. Literally did not play even one Shaman, Hunter, Rogue or Warrior last night.
Regarding the meta in the ladder, HS has a huge long-term issue coming from new players (there are other issues, too, obviously, but this one is, I think, one of the most important).
I guess you all know the argument that a big reason why aggro decks (and quicker decks in general) are / were so favored is that all other things being equal, an aggro deck takes less time to lose or win and so it is more efficient than a slower deck - you can play more games in the same time period, that results in more rewards (especially below rank 5), etc, etc. They had to create entire mechanics (*cough* LOE *cough*) to fight that somewhat.
It goes much further than that and there are other things that work in the same unhealthy direction.
Think about new players. They have no cards, right? So, in order to stand a better chance against players who do have cards, they have to minimize the number of cards that get played, right? Because their cards are just worse than cards of their opponents and so each card that does not get played is a win for them. That's a very powerful reason to go for straightforward *quick* plays and ignore 90% of what could have been called "strategy". Because quick is a gain in and of itself.
Further, think about new players again. Again, they have no cards. So, what else can they do to maximize their chance at a win against players who do have cards? Why, of course, they could go for high-RNG moves. The more RNG you plug into your deck, the better. A portal is better than any other card with the same cost, because it's powerful RNG and your rare chance to play like big boys play. Things like shaman's 4-7 damage ranges are just superb, you put them in the moment you get them and hope to get a 7, because that actually maximizes your chances, you don't have cards to play with low risk.
Etc, etc, etc, there's a lot to write.
This is a no-win situation. If the game stops getting lots of new players every month, it will just die. Because it's a mainstream game, that's how mainstream games work, they constantly lose players and have to compensate for that with constant gains of new players. So, the game has to succeed in getting lots of new players every month, and these players put the meta under heavy pressure - and it does not stop at rank 20 or even rank 15, it propagates everywhere, because quick / RNG / etc decks is where new blood is and where the innovation is.