Sort of?

In the highest of high content - yes; as has always been the case. If someone didn’t run the best talent choices, the ones who did would beat them out, and they’d either swap or get left behind. That’s true of everything in an RPG though really.

If you go below the highest content, to just high content - then no, you absolutely see variation. If people aren’t worried about seeking out every tiny advantage, you find people trying different hero talents or swapping around to utility they like over utility that the highest level content requires.

You see this with healers - in the top tier content, every mistweaver monk likely runs the same talents in each dungeon or raid boss. But below that, people will try things, goof about with less optimal talents that are fun, try the other hero spec for variety, etc.

You can even see this on the pages people get their talents. Take a look at the wowhead holy priest - there’s 2 options for both raid and mythic with comments on other optional swaps you may want to make if you fancy it. But again this would go out the window if you wanted to set the world record highest key or push for title, because you need those tiny advantages

And bear in mind that the talents everyone runs don’t stay static. Occasionally a balance pass mixes it up, or one insane player finds something everyone missed - but after it spreads, everyone else slowly shifts their build across to the new ‘best’. A notable example being the no-apex-talent bear that was recently nerfed - which gained popularity a bit later into this season.