The thing is, Melvins have always worked well for me because it's very simple music on one level. There isn't a lot of obvious "skillful playing", soloing, or any of that shit... at least not until Mark. All of a sudden, especially on Stag, there's bass noodling all over the place, specifically obnoxious runs up and down the scale that annoy the hell out of me. I wish he'd have learned to just shut the fuck up and play the bassline instead of showing off that he also knows how to use the other two strings on the instrument.
Moral: Never EVER get a guitar player to play bass. It can only go wrong.
Thankfully he's left the band in the meantime.