Dish is the lateral positioning of the rim over the hub and axle. The rim should be centered between the axle-ends, which means it won't be centered over the hub-flanges. To test this centering, take out the wheel and flip it around (swap left-right sides). The cogs will be on the left and the chain will be resting on the hub-shell.
How centered is the rim now? I take it you have horizontal dropouts if you can adjust centering between the chainstays. With the wheel flipped and centered between the chainstays, how are they between the brakes? If they are rubbing on the other side, then the wheel needs to be dished (centered between axle-ends). If they are still rubbing on the same side, the rear-triangle may be mis-aligned or the brakes may be off-centre.