The Runed Fighter's Staff is the best weapon in the game currently. It's the best and highest damage per second of any weapon because of damage bonus. This is the reason it was removed -- Insane DPS. First they removed it. Then they altered damage bonus on two handed weapons under 28 delay (There were no other two handed weapons in the game at that time under 28). It was just too powerful. This is the same reason why the Moss Covered Twig and Barbed Scale Whip were moved to off hand only (Off hand damage is (Offense + Strength) / 100 x Weapon damage -- No damage bonus).
Prior to the patch here, all two handed weapons had the same damage bonus.
http://www.tski.co.jp/baldio/patch/20000919.html
I haven't had a chance to parse both of them (No T staff currently) but I would venture a guess that the RFS does about 15-30 more damage per second than the T Staff. They are basically the same ratio but the RFS has 10 less delay. You simply have more chances to hit with it. For every two rounds you are applying the damage bonus with the T staff the RFS is getting three. Factor in double attacks when you don't miss and thats an extra 34 damage every second or two with max haste.
Would like to have someone 50+ with both weapons post here to see how much more it really is.