I had this problem with my last band, and to an extent with my current band, although I was able to use a lot of the same tricks over again. I found that it was a combination of the things listed: cab position, EQ, and volume. Get the cab pointed right at your head, and use enough volume that you can hear it in that position. Also, this sounds contrary to logic, but stand a little further from your cab - especially if it's a closed back, those things beam like crazy, so if you stand further away, your sound has a little room to spread out, so if you move a little bit, you don't step out of the "sweet spot". Also, I had to EQ some bass out of my tone. The bass player covers that, and the thinner sound cuts more.
The main thing I've found is that a band that is pumping a lot of volume but is confined to a small stage, is never going to have a good mix right on the stage. The cabs are too directional to get a good spread in that amount of space. Just have to either get the mix right in the listening area, where things will even out a bit, or let the sound guy sort it out if everything is mic'd.
Obviously, the real solution here would be to have a chat with your band about playing at a more reasonable volume. But I've been there, with dudes who just have to play at 11. Really frustrating when you know the music is a lot more enjoyable for everyone when it doesn't cause a headache!!!