I agree with the slight muddiness overall.
The groove is cool and all.
There are two things that bug me about the vocal a bit:
1. It sounds a bit shrill. I think it could use a bit of EQ to tame the high mids a bit.
2. I don't know if you can do anything about this, but the vocal tone sounds a bit thin. It's hard to describe ... you're (or the singer is) hitting the notes (the majority of the time ... there is a little pitchiness every now and then), but the tone sounds a bit weak ... as if this key is just really too high. It doesn't really sound very natural to me. It kind of sounds as though it's too much falsetto with not enough chest mixed in, so it doesn't have the power that Brian Johnson has with it. Maybe his voice is just higher in general, so it's a bit easier for him.
Like I said, I don't know if there's anything that can be done about that, except lowering the key, which, of course, is probably not an option at this point. Believe me ... I couldn't come near to singing that high, so I feel your pain. But it sounds as though it would be much more powerful if it were lowered a whole step or two.
Just my two cents.