An amp like this does need individual bias trimpots unless you are a rich man.
The 6550's are "special design" selected Tung-sol's and matched as an entire set. Pushing them pretty hard with a plate voltage of 700VDC.
"bias set for total ~210mA", is about 35mA each for 24.5W quiescent. With cathode resistor 10R, for 0.35V each. You're getting from 30.4mA to 51.9ma?
Those tubes aren't matched that great, well enough to work here or there are damaged screen/plate resistors. The OT asymmetry is not the problem, it's not going to make the Q-point that far out.
You have to at least get each side (set of three on OT leg) closely matched so you can work with the balance pot.
I would set the bias equal and measure then sort the tubes by cathode current, then shuffle them in each side so that is best matched, then do the bias balance to bring the entire set close together. Otherwise, you will just bake the tubes having higher transconductance and it will be in the shop again.
Having mismatched tubes between each side does affect distortion, but Fender does not allow any other way to set bias.