I agree - doing these under "interview conditions" is a farce. It tests for other attributes which are probably not relevant to the job (and not a good thing if they are).

Then stop asking these questions. During an interview you should be determining if a candidate is a good fit for the job they're going to have, talk to them to suss out their fit with the existing team and maybe bring up a few issues you recently hit in your day to day work (or that were recently hit by people doing what this hire will be doing). A beautiful hidden point in this, assuming this task wasn't solved entirely in isolation by one person then discussing what the company did after hearing their thoughts will demonstrate the sort of communication levels the candidate could expect if they accepted the position.

By asking rote questions like this you're much more likely to decrease your chances of getting people who are good team builders as the lack of a focus on team cohesion will turn a lot of people off.