You're reaching here. This can happen to an extent and maybe NRS is "special" as a working place where things like this can happen.I don't think so. If someone with a big enough voice in the community can complain incessantly about a character and receive a comprehensive package of unnecessary buffs (Kenshi in MKX), who's to say a tester can't do the same thing and maybe even have a stronger influence on the designers since they are under the same roof?
I can only speak for the company i work in and while - sure we meet some QA testers over lunch or coffee breaks here but there is no way i even know 1/10th of them and i work here for over 20 years now. QA testers (temps) change like every few to several months, people rotation on this position is crazy. Only a pretty small amount of people work as full time QA testers here and granted i know most of them but i wouldn't say i take feedback from them.
We have over 400 employees here, we work on different floors (QA is at the bottom) and what is most important here - EVERY change in game that is made in ANY source code branch (QA for example has their own source code branch, even several) MUST be fully explained - documented and is seen by EVERY person with access to that branch which is a LOT of people.
Even IF one of the game designers (influnced by one of his QA friend) wanted to push (lets say for the sake of conversation) a change in game: reduce Cetrion ground boulder startup frames to 10 and even if head of the department would sign off on that you still need to get an OK from lead game designer - for it to go into "live" branch. I'm also 99.9% sure that other game designers would question that change even before it would go to the head of the department or later to me (or other lead game developer).
You also forget that most if not all game designers, lead game developers play their own games. Like seriously play them, on top of watching people play them on streams etc... Most people also tend to think changes in character balance are made for hardcore "competitive" players in mind only and that's true to some extent but not to all cases. Some changes make sense from the design standpoint, visual standpoint, gameplay standpoint but they don't make sense from competitive standpoint and that's OK, they still go live. Games are made for all people and casuals make roughly 70 to 98% sales so if we make them happy by changing X to Y we're ok with the 2% - XX% who won't be happy with our decision. That's just how it goes.
If you want to think about how things work in game industry in general always look at the broader picture and from where the money comes - first and foremost. Money comes from casuals.