Is the 6-minute bard diet still 6 minutes?
 

So I haven't had a crack at the bard quest NPCs for ages until this morning on an alt...and it seems these guys aren't respawning every 6 minutes anymore.

Was this updated to reflect classic? Or are the one I tried in Feerrott (the one that pays best per kill) and Nektulos (near somewhere I can sell) just bugged? When was it changed?

Try red man the dungeons are empty no need to bottom feed on bards.

IIRC some of them were changed within the last 1 or 2 years to be more accurate with live.