IMO the gold standard to judge a set or meta in a year is to look at the WR of all tier 1 decks in the field, and I guess it is what HS is relying on urgent nerfing. As long as their max WR is around 65%, then the dev will not border to change something.
my 2nd point is, HS dev has its plans on rotation of strength of classes. Some class will stay strong across the whole season because of this plan.
and the last thing is, there is a planned Spell Lock event in the coming seasons, this may be something that will change strength of classes significantly
Why there is a rotation of class strength?? may be HS dev want everyone to learn every classes more thoroughly :P~~~ This benefit HS profit, players, and also the game itself.