Overwatch's development team has a reputation for being very open about the direction of Blizzard's competitive shooter. Be it balance, content or in this case, the metagame, game director Jeff Kaplan will usually provide a thorough reply. Just yesterday, Kaplan penned a 2000-word opus, responding to the desire for players to see "'radical' balance changes to mix things up".
Replying to a post asking why Overwatch's balancing cycle is "excruciatingly slow", Kaplan delivered a detailed explanation of the developer's approach to updates, particularly those that could massively affect the metagame:
I’ve been reading the feedback regarding the current metagame and a general desire for “radical” balance changes to mix things up ... I like when the meta changes on balance only when the game is not balanced and something was adjusted to make the game more balanced. Another way of putting this is, I do not agree with the philosophy that we should just make balance changes solely to shift people off the meta.
Kaplan says he's not a fan of "balancing heroes just to make them picked more or picked less" and while a character being considered too strong or weak can contribute, overall the developer makes changes not to buff or nerf, but to simply "make the game better".
The post is extensive and difficult to summarise in a couple of paragraphs, so if you're at all interested in how Blizzard (or Kaplan) approaches Overwatch balance, this is the manifesto you've been looking for.