In the intro to the Scorpion. Part I episode, we see a Species 8472 bioship attacking several Borg cubes. Their bio-lasers have absolutely no problems in penetrating Borg shields and completely destroying each cube.
Later in that episode, The Doctor explains to Kes, that each Borg assimilation starts with piercing a victim with two assimilation needles and injecting nanoprobes. Upon Kes' proposition to use some kind of force-field or shield, the Doctor objects that no known material, force-field or any other solution is capable of preventing the initial piercing.
I have the feeling that these things contradict each other. How can it be, that Borg created a material (clearly a metal sting) that can't be stopped or blocked by anything, and at the same time, they're unable to create anything, that would stop a bio-laser?