I don't think most of the entrants expected to succeed, so that's not too big a surprise. Even in a "runnable" 100 mile ultra marathon, only about 50-70% usually finish the race. You can see some stats here:
The same race director puts on a much more finishable race - 314 miles, typically self supported, in the middle of summer, across the entire state of Tennessee:
I understand race preferences are idiosyncratic but what about Vol-State appeals to you? Distance? Crossing a state? Laz?
If anything on your list includes something in Colorado (or Bighorn or Fat Dog this year) send me a note--pacing is sometimes more fun than racing. (Same goes for anyone else reading this).
http://run100s.com/ultra.htm
The same race director puts on a much more finishable race - 314 miles, typically self supported, in the middle of summer, across the entire state of Tennessee:
http://ultrasignup.com/register.aspx?did=29688
It's on my list of runs to do.