I have stumbled onto pure gold for a "dual cab" configuration.
Channel A use Uber 4x12 + 57 on axis
Channel B use XXL 4x12 + 121 Ribbon
Set Channel A volume around 45-50%
Set Channel B even or a bit less than Channel A. I find -5% works well.
Set the Cab DEP's all around 25%.
Don't use EQ's after the amps and before the mixer - this will cause phasing unless you apply the same amount and kind on each Channel. Use a Mid-Focus EQ after the mixer and set the HP freq to 15% and Q to around 25-35%. That should tame some boominess. You may have to use more midrange or highs than usual to get it to have enough.
This is the most realistic tone I can get. It's not just the sound - it even affects the feel. The response is super crisp. The tone is thick and resonant. Highs are crisp. Sits perfectly in a mix. The tone has a nice rough edge to it too.
if you got a mid-focus eq in post-mixer placement, you can just set the hp freq between 12 and 20% and keep adjusting Q lower and lower and adjust the freq until you don't get any boom, but it sounds natural, and it doesn't sound thin. If there's too much roughness to the distortion, you may have too much bass from the guitar that a boost or pre-eq isn't downplaying, or be distorting the power section with a lot of bass on the amp control. Same goes for backing off the mids and spiking treble. When you turn up the master volume d.e.p. things start getting awesome, but can quickly turn to into a dying pickup truck, if you don't have the entire signal chain under control.