I really like the mix on God Forbid's last couple of records! Never noticed them being muddy?!
Another "I forgot"... Megadeth. Rust In Peace. It's not the mix so much as the tones. Thin, boxy guitars (isn't that album Bogner and VHT? That's downright embarrassing!), the bass tone has no bottom, and... well, I guess the drums were probably alright in the room. I like generally like dry drums, but the drums seem to suffer from the same problem as the guitars. This is the original mix I'm talking about, mind you; I haven't heard the remix/remasters and I'm not sure I want to. I like the album, but it just sounds so... not heavy.
I don't mind Rust In Peace, wouldn't say its particularly bad - So Far, So Good, So What? on the other hand.....
If looking only production wise, without concerning the musical content:
Metallicas ...And Justice For All, Ride The Lightning, Kill Em All, and St. Anger in that order. Those albums really suck productionwise. Master of Puppets, Black and Load/Reload are still one of the all time best sounding heavy metal records on any standard.
And Vio-Lence - Eternal Nightmare is quite awful too, some of you might know guitarists from their current band called Machine Head.