I did shoot a roll of Velvia last fall and it was pretty disastrous. I had thought the lens just didn't handle color properly. From this test it's pretty obvious it was the photographer's fault.
For slide film I would suggest you upgrade your Mark-I Eyeball Sunny 16 light meter (which is generally sufficiently accurate with negative) with Any Brand can Work SBC incident light meter. Your results will miraculously upgrade from pretty disastrous to pretty well exposed as well