I’ve watched video of it and it looks tough, but how strong do you need to be to get over the wall?
8 strong!
You don’t have to go up the Wall. You can go around and many riders do, including some Pros.
Go to http://www.savagemantri.org/2008_video.html, scroll down to Part 12, which shows the tail end of the race going through, and take a look at the dead last rider go over starting at 2:55 in. No more music. No more fans. No more glory. But just watch her go. That should answer your question.
Note, it ain’t the Wall that makes the race SavageMan. It’s the next 6 miles of climbing after the Wall, and the multiple climbs later in the race at >13% and >1/2 mile in length.