I completely agree that if you're designing an sort of assessment process, you should go through it yourself or ask other engineers to go through it so it's reasonably scoped in terms of expected time commitment. You can also use assessment tools that specifically limit how much time an engineer can invest in working on the challenge, which is also useful in showing how much progress each candidate made in a set amount of time. The problem with this approach can often be that the candidate feels like they're working against the clock though, which isn't "real world."