Clicking through the results, it looks like more than 2/3 of the participants DNF'd. I've never seen anything like that. Your 18:50/k looks pretty good!
Tough navigation, tough terrain, sub-optimal weather - a bit of a perfect storm. Plus, there were snakes, although I seem to be the only one affected by that. Even Boris didn’t quite break 10 min/k.
The DNF rate would likely have been substantial even in good weather since the terrain is a major shock to the system of many QOCers who have little experience with anything but spur and reentrant terrain but the ~half hour of downpour, with a bit of thunder and lightning that scared a few beginners into abandoning their courses, starting almost immediately after the courses opened definitely made things worse. Unfortunately, having a shorter/easier set of courses ready to go in case of bad weather would blow the already substantial effort required to put on an event up beyond reasonable limits.