In our rehearsal room the lead guitarist has an Ashdown 2x10 amp and a Marshall 4x12 half stack.
Every so often I'll really be struggling to hear myself clearly. After upping my mids a bit to cut through, then usually upping the volume, to no avail, I'll ask what amp are you using? Yep, the Marshall.
It's not the volume with it, it's the frequencies it's taking up. It seems to just cancel out my bass, which I don't have as a thundering bottom end, more clean and punchy.
I bet if he took some bass out of his EQ you'd suddenly be able to hear yourself without upping the volume.