The shaman "Spirit of the Puma" (PoP+) and other such proc spells generally have a modifier (think highest is 500%). Some weps also have proc mods but outside of this one I'm drawing a blank atm for classic weps.
http://everquest.allakhazam.com/db/item.html?item=274
tem Type: 1H Slashing
Light: Tiny Glowing Skull
Stackable: No
Proc Rate: 389%
Submitted By: Jozona
Lucy Entry By: Agamenoar
Updated By: Roadmeister
Source: Live
Updated: Thu Oct 9th, 2008