I mean, it's pretty obvious the Borg got hit with the nerf bat in VOY, but Dark Frontier makes it almost too fucking hard for me to watch. I mean, the bio dampener of the Hansons which was also used by the Yoyager crew isn't a cloak, right? But, uhm, the Borg have bloody eyes?! In fact, they even have supposedly better eyesight through the cybernetic implants. Borg drones can hear as well (and the scanner of Janeway makes noise), or smell. In the finale of the episode, Janeway enters the "throne room" of the Borg Queen who immediately notices her, because, of course, she has eyes. I really wonder why they decided not to make the bio dampener a cloak, they made the same logical mistake with the Delta Flyer's "shield modulation" which supposedly hides them from their sensors, but isn't a cloak, but on the Borg Queen's viewscreen the shuttlecraft just vanishes, as if it was cloaked. Technological wise it also isn't such an ingenious technology, considering even contemporary military works on technology to shield soldiers from heat detection.
One possible solution would be the fact that the eyesight of a drone would function completely via their neural implants, like an artifical eye, with the biological eye being replaced, and that the optical implants can't process biological life as such if their life signs are dampened. If this would be true, this seems like a horrible flaw of the Borg (and there are quite a bit already). And even then, you'd assume that they can input a command to put the optical implant on stand-by and order the drones to use their "normal" eyesight again. I mean, in the episode where Seven of Nine got stranded with a few other drones on a planet, they start cooking food and other stuff as an emergency back-up routine that is activated when isolated.
Don't misunderstand me, it is still a good episode, because the looming dread in this two-parter, that is really well done, and it probably has the most horror movie like scene in all of Star Trek (Seven witnessing assimlation of a species as they scream and cry in pain in the background and she watches them being mutilated), which makes it one of the best Yoyager episodes, but this really puts me off it. I assume this is another case of inventing an "off-trigger" of a villain that the writers created to be too overpowered, but I always think of Post too long. Click here to view the full text.