Hey there found proof of what it's suspose to do from a 03/2001 wayback search:
https://web.archive.org/web/20010305...s/level_49.htm
Shaman spell "Rage" (level 49 spell):
100 mana
18m (duration)
+ 51 Dexterity (60 max), +51 Strength, +18 AC, +51 Agility (55 max).
Self only, no spells may be cast for 6 ticks.
Update: looks like it gets changed to the above on december 2000 (release of Velious)