I've got this second-hand Roccat Isku. I really don't like typing on it, but that's me. It's a pretty standard rubber dome action and there are no surprises inside the case.
On this particular one, the "W" key is non-functional. Given the target market of these, I'm not surprised the W key has taken a pounding. I took the back off to take a look inside, in the hope that whatever has broken will be visibly obvious.
Once all the screws came out (including the many hidden under the rubber feet), the back came off easily to reveal a white backing layer (presumably the source of the key illumination). Beneath that, three layers of membrane, and nothing obviously wrong with the "W" key or associated membranes; looks just like all the rest.
A few solder blobs are not the tidiest pieces of work, and there's some white residue on one of the electronic component mounting boards, but nothing too horrific.
Low-res pictures:
I expect I'll give it a hosing down with the compressed air, put it back together and see if just the act of taking it apart and putting it back together did any good.