Individual bias usually only allows you to use unmatched parts from the same manufacturer and preferably from the same lot number. Gain at DC and gain at HF are two entirely different things due to internal element size, spacing and capacitance. Don't just assume that because DC bias voltage has been set differently to achieve the same idling current, that the full operating current under RF load will still be balanced. That should be measured and confirmed just like the idling current was. If a tube was drawing low idling current because it was weak and you turn up the bias current, it still will not do its share of the workload.
Remember, this modification didn't offset the RF drive voltage like it did with the DC bias to reach balance. Balancing only the DC current and ignoring the RF drive voltages to the tube will not allow you to do something like run a GE 6LF6 with a Sylvania 6LF6. The internal differences within the tubes are enough that the harder you drive them with RF, the more out of balance they will run, even if they start out at the same idling current. The more the DC bias voltage has to be offset to obtain equal bias current, the more this problem will become an issue.
PS: I can make a weak tube draw normal idling current by adjusting its bias voltage but it will still NOT do its share of the workload when amplifying RF due to a lack of peak emissions.
