Source:
http://www.tski.co.jp/baldio/patch/20000217a.html
Date: FEBRUARY 17, 2000
Mistwalker:
The Mistwalker will once again cast its spell as often as it used to prior to the last patch. However, the resulting pet will now automatically "dissipate" after one combat round. The change that reduced the "proc" percentage on the weapon was made due to an unintended interaction between the pet and the target when several users of this weapon were attacking the same target. Since the new pet now automatically dissipates after one round, the reduced "proc" percentage was no longer necessary.