I disagree.
I think a deck being very popular is NOT a bad thing. A deck could be 30% of the meta and that isn’t necessarily a problem. It could be a problem, if that deck didn’t lead to a wide variety of different game states. In other words, a deck that is popular and consistent can be problematic, because it’s frequently encountered AND it’s (pretty much) the same thing every time. That becomes repetitive, and gamers have a love-hate relationship with repetition.
But really, I am not trying to single out “diversity” here. My core issue is that fun games are fun and diversity is NOT the same thing as fun. Whenever a game developer starts to pursue a design vision that tries to simplify fun into a different concept, then myopically focuses on that concept, fun is often a casualty of that dogma. Sometimes diversity is fun, sometimes it isn’t, and ultimately you need to look at the audience, get their feedback. Fun is an inherently subjective experience, and you can’t boil it down to an objective measurement like “5% popularity or lower.”
If there is a concept that I think is important to fun, I think that concept would be audience levels. I think players at high skill levels have significantly different tastes from players at lower skill levels. I think the core difference between high skill and low skill is that a high skill player can look at a board state and see several effective options, with an engaging internal debate within themselves regarding which is best, while a lower skilled player can look at the exact same board state and not see those options at all. In other words, a higher skill player inherently experiences a more dynamic environment with more options.
I think that diversity of experience is therefore way higher of a priority for less skilled players. I think that decks that are “consistent” should be designed to be difficult to play, and that decks that are more streamlined and easier to pilot should have more random effects to create less predictable board states. I don’t think it’s a problem for a deck to have double digit popularity in top Legend, because players at that level can, do and should change decks to counter anything that becomes too popular; at lower ranks, this kind of metagaming is not as enjoyable, so people don’t do it even when maybe they should, and it should NOT be expected of them. (This is one of several reasons I think balance at Diamond matters more than it does at top Legend; if anyone deserves to be told to suck it up and git gud, it’s them.)
I guess what I’m trying to say is that, if I had to pick one sign of a healthy meta, it would be that the top Legend meta and the Diamond meta wouldn’t look alike. When they do look alike, it probably means that one group is getting what they want, and the other is stuck getting what someone else would have ordered. Decks should purposefully be designed to function differently at different levels of piloting skill, and as one climbs one should go through metas that feel substantially different from each other.
TL;DR nerfing Sonya Rogue was a mistake