When I see people mentioning fizzbuzz, it's always to filter out people who really can't program. If you just give me ten minutes to solve a fizzbuzz-like problem, that should be plenty of time for me to solve it given that I do know how to program, and just that single test would be enough to filter out those who don't. I don't see why it would have to take several hours.
Multiply that by the number of companies you are interviewing and that can easily be 8-15h in total. I'm glad I didn't have to do that.