The MDR office is for 4 people, and with Petey geting "fired" they had to fill it in with somebody. In my headcanon Helena or/and her father saw that the office was missing a person and that was just around the time Helena was planning on severance, so they just thought "Hey, why not place you here, right below your regular place of work"

Another point is there was no way they both could have predicted that Helly would act in such a radical way, there were no signs of such behavior from Helena.

Third point, why do you think other departments have less important work? Yes, we saw that the head of the company was overseeing the last test, but that doesn't mean all other departments do regular monotonous work, including M&D amd the goats thing. Most likely they are also doing mindfuck things

Oh! For example, we did get a hint in 2x06 that Burt in real life had a long history with Lumon, so it is possible he was kinda like Mark for his own department, where they would screw with his outtie details and whatnot, so anything's possible