I don't think the devs are particularly concerned about about "OP" builds. I think people are convinced that the developers care about things being perfectly balanced across all builds, which... no? If that was the case, you wouldn't have feat choices, you would just have a single progression pathway. Now, there are some things which might cross the line into *exploits*, which I'm sure the devs do actually care about.
I think, though, the developers do feel pressure from people who *think* builds are "OP" (in a primarily PvE game, which people can play more or less entirely solo) who then write long rants about "X should be nerfed" and "Y should be nerfed". But those people are usually just spouting hot air. I've sat down and run actual numbers on things and people just shrug it off, even when it proves mathematically that a feature is not as powerful (or as weak) as they think it is. Now, I assume developers can see that, for sure. They have access to things that I don't with regards to logs and completion times and so on that, while not perfect metrics, can help assess things across different builds in ways I simply can't around a ton of soft factors, though I don't know how robust the logging is.
But in the end, it doesn't matter- if the community begins to repeat that certain things are overpowered, even if that's not what happens in actual play, because someone who thinks they're running The Best Legit Build which anything stronger than their build is clearly cheesy OP shenanigans is in a dungeon and has their sensitive ego bruised by someone getting more kills or tanking a hit they can't or having crowd control which they didn't get or just having more fun than they do, it gets shouted and repeated on the forums. Part of the reason why some balancing efforts in the past have felt heavyhanded or inaccurate to the community is because either they're responding to a problem that doesn't exist, so actually fixing it is impossible because there's no problem and any nerf is too strong or they're looking at logs that show an actual overperforming feature and adjusting that instead of what people have gotten into a frenzy over.
However, the only argument for "strong" builds making the game worse depend on either the game being balanced around outlier builds or someone's fun being ruined if someone else can do something they can't. And some of that is fair- I mean, look at the spike between "old" and "new" heroic content, for example, there's an era where heroic content is significantly more difficult than even the epic versions because of poor heroic balancing around... power creep? Nver actually figured that one out. But unfortunately most of it just feels like someone looking at someone else having fun and not liking it, or feeling like they have to play an optimized build to have fun which simply isn't true and I've enjoyed a lot of my more interesting builds more than cookie cutter "optimized" builds. While exploit/bug fixes are probably fine- after all, there is a difference between "strong" and "broken", even if it might mean for a weaker build- reactionary nerfs don't feel great and they almost always stem from forumites, and often seem to be based on very subjective comparisons between characters instead of actual experience- "Casters are OP" is a common thread, but you usually don't see anyone complaining about the average caster build, just the ones that involve a lot of complex build crafting and itemization.