I now think the uneven waves seen in the test print actually have to do with the printer alternating between draft, high quality and NLQ.
If I print a page from GEOS, I don't see that dramatic of a difference from line to line. I'm still getting some slight smudging but I find it to be acceptable for the time being.
If you take this photo and look closely (potentially zoom in) where it says "nose to nose" in the first line, then look straight down from there, that area of the page has that weird smudge going on which frankly may just be an artifact of this almost 40 year old printer.