If you had a character that can swarm, you could PL that character fast to max level. Then come back and use the swarmer character to PL the other 5 characters really fast. SK is a great swarmer, and a mage Beam kiter is really good. Swarming is how most PLing is done in EQ1 right now.

Google SK swarming or mage beam kiting, or go to youtube and watch vids of it being done.

If you don't want to go the Swarm or Kite way, you can maximize experience by playing on the FV server(RP and all raid drops sellable) you get an 1.5 times experience bonus for characters. I play on the Test server and automatically get double experience, plus I bought a 50% group experience potion and copy it over to Test for extra experience regularly. Besides potions and server experience bonuses, there is an veterans AA that gives 50% experience bonus and is free if you earned it or is free on Test if you earned it or not .