Peter,
As promised, I've finally gotten round to listening to the files linked to above on my humble Tannoy Actives.
I played your mix first followed by the other mastered version.
Now it may be that I'm just not that familiar with the genre (about the heaviest I got back in the 70's~80's was Sabbath plus a view others) so I probably don't know what I'm talking about.
But I still prefer the "mastered" version although I'll conceed that perhaps the reverb doesn't suit the vocals to much... needed to be even more subtle.
I still feel that the guitars in your mix is overpowering things just a fraction too much. I agree that four layers of guitar would be better but I'd still bring 'em down more. Sounded to me like some of the guitar parts were fighting for the same space as the drums particularly at the lower frequencies. I must add though that my ears are still as yet untrained especially in listening to a track in a more critical manner than I would normally so you should take what I say with a pinch of salt.
I'm going to have a mess with my version now just to see what I can come up with and I hope to have something for later this evening (my time).
Later
andy