Hi.., I often get confused by various terms, i.e., 'drag' when it comes to moving parts. That said, 'slip' is a term often used when clutch plate is contaminated with slippery stuff. That would be apparent going up hill, when although the rpm is correctly steady, the vehicle begins to slow down, i.e., the clutch is slipping, and can't maintain proper road speed to match rpm, often requiring down shifting, perhaps several times in order to crest said hill.
I have had the above issue with an oil soaked clutch plate. Old school remedy is to fix oil leak, and then lay clutch plate on the ground pouring gasoline on it, and tossing a match onto it, and burning off oil.
Somehow, given all the bullet-proof reviews of the AX-15, I would not think your syncros are shot because of a 'rear main seal' oil leak, for your internal transmission parts are all gear oil soaked to begin with. Your symptoms of 'dragging', or perhaps 'slipping'/'slippage' is indicative of an oil soaked clutch plate. Pressure plates with weak springs could also be an issue.
Me.., I'd just replace clutch, and pressure plate 'set' with some heavy duty brand, and also replace clutch slave while transmission is out already, anyways.., and fix the oil leak at the rear of the engine, replacing the RMS, and Valve Cover Gasket.
WinterBeater is giving you a place to consider, i.e., clutch bleeding.., which is to say put everything back together, and bleed it, (if you hadn't already). If that then fails to work, then replace the slave.
If your co-worker suspicions bother you, you could take your tranny to a specialist for a check. Thats akin to a third party diagnosis, allowing them to correctly deal with it, without the guess work so far done clouding up the good intents attempted. Should not be too expensive, couple hundred bucks for labor, plus parts. (if they can't replace clutch/pressure plate, and clutch slave in two hours they are cheating you).