Comparing to the human brain is primarily connected to failure option 2, not option 3. We've had many years now to make computer systems and general algorithms that don't rely on human architecture. We know that machine intelligence is behind humans in many areas but we also know that computers are well ahead of humans in other areas (I'm pretty sure that no human on the planet can factor 100 digit integers in a few seconds unaided). FOOMing would likely require not just an AI that is much better than humans at many of the tasks that humans are good at but also an AI that is very good at tasks like factoring that computers are already much better at than humans. So pointing out that the human brains are very suboptimal doesn't make this a slamdunk case. So I still don't see how you can label concerns about 3 as silly.

Cousin it's point (gah, making the correct possessive there looks really annoying because it looks like one has typed "it's" when one should have "its") that the NP hard problems that an AI would need to deal with may be limited to instances which have high regularity seems like a much better critique.

Edit: Curious for reason for downvote.