A more inflammatory take than usual, Mfauli.
Glad you found a dub that fits your preference better. It seems the Japanese VA industry has vaulted ahead of its western contemporaries (or maybe has already been there), as it really pulls in some star power over there. English dubs are getting better, but slowly, use many of the same actors, and still have the regular stinker here and there.
The violence isn't realistic. Nobody found the child being afraid of the villain funny (it was framed as fear), and as has been mentioned, she has been desensitized somewhat by her abusive upbringing in the lab and elsewhere in the orphan circuit.
It's shown, not glorified. Just a stylish exposition/introduction of the character, not an endorsement of killings. "This is who Yor is and where she comes from. She has some mental issues". Take it like the story telling you that and you might find more enjoyment. Her character design is cute, though...
Is that necessary? To pre-emptively dismiss an entire audience for having maybe different sensibilities than your own undermines your argument. It comes off as virtue signaling, and no good discussion is had from that.
I'm sure her backstory/work will come up again, and guess what? It's probably going to feed into some jokes that involve people dying; I hope they don't put you off too much.
So far it appears to have, even the filler is fun.
Good observation; I forgot that she acts like there is a 'switch' to killing mode. I don't know if she enjoys the act of killing or if her fulfilment is more akin to satisfaction in a job well done, like when you finish a cleaning job that was overdue you feel a load off your shoulders or the like?