It cannot be stressed enough that this is a prime example of how not to make a scenario.
Giving Selentine the benefit of the doubt, it looks like the kind of thing someone would do to simply familiarize themselves with the engine, its' basic scripting, and its' editor's most basic functions.
With minimal scripting, no balance in combat, essentially no plot, a single side quest, and a playing level clearly out of the stated parameters, Nephilim Valley gives the impression that the author threw down a handful of purely functional maps (including one that looks as though it was mostly created with the "change terrain randomly" tool), loaded them up with low-level items and average-level monsters, torqued exactly one core stat and the item loads for those average level monsters in the scenario data script, and then released it without testing.
While the author does thank beta testers, and while there is slightly more scripting ands design than this, the lack of substance and technical savvy, combined with outright torturous gameplay leads me to rate Nephilim Valley as [rating]Poor[/rating].
All that said, if you're the hardcore hack-and-slash type, and have a well-equipped party resting above level 75, Nephilim Valley could prove to be an amazing tactical challenge, as I'm sure was the author's intent.