http://www.tski.co.jp/baldio/patch/20001003.html
Right where I expected it to be based on the evidence so far. October 3, 2000
Ragebringer nerf, alongside NPC and Quest updates. Based on the timeline I think this makes sense as the starting point for the behavior observed in Plane of Hate. It was the last patch before it was reported, and the only other patch between epic implementation and the report was Sept 28 and was a lvl 1 name purge, fix to fleeing NPCs, and some command and UI tweaks.
http://www.tski.co.jp/baldio/patch/20000928.html