This is intellectually confused. Dahj was superhuman. There's no realism issue.
How should a superhuman combatant pitted against a bunch of normal combatants look?
I get that, but as an audience, we're used to seeing regular humans pulling off these superhuman-like fighting feats. So seeing a "synth" do the exact same onscreen isn't impressive, even though it makes sense within the story. And on top of that, the way it's portrayed is something we've all seen before, whether it be in the various Bourne films, or the MCU.
And in addition, we don't get any emotional consequences or mental repercussions for the character. It's meant to be cool though for the series opener.
Now we get Elnor providing similar type of awesome action. Just prior we had Picard being cool and having guns stashed all over his house, something we've seen plenty of times in movies, and him and his house keepers kicking ass.
But Elnor kills someone, hey that's wrong.
But he's right back to kicking ass in the Borg cube. "Picard, I can't go with you because I have to stick around and kill some more people. It's my thing."
I still like the show and maybe they'll address it. But in the meant time it's something I find fault with.