Missing Low End in the mix

As already mentioned, the low end in a mix comes almost exclusively from the bass guitar and kick drum- there is no advantage to EQing the master bus instead of just focusing on those two tracks. That kind of makes it like you're playing the mastering engineer, and you're fixing a mistake the mixer made...except if you're the mixer as well, it just makes no sense. If the 3dB boost you mentioned sounds about right on the master bus, then that means you should probably turn up the bass guitar volume about 3 dB, or maybe just make the same kind of low-end boost on just the bass guitar track and a bit on the kick drum.

Good point. However, I only had to add the bass in on the master because I used a multiband compressor on the master, which took out a little bit too much of the lows. I probably could have adjusted the multiband to not take out so much, but Multiband -> EQ worked fine.

This was my Mastering session with one stereo wav file of the mix - mixing was done.
 
Haha wow I didn't realise Maxxbass was so frowned upon...anyone care to back up their slagging with some reasonable info?? I'm always open to new ideas. I just found it gave my final mix exactly what it needed (when used fairly subtley ont the master buss) and sounded like what Mendel might've needed...glad you found it better than rbass at least!