does +20% Spell Damage work?

So I just spent my life savings (literally) on an Enchanted prism staff:
Lvl: 40
Damage: 392
Value: 750360
Equip Bonus: +20% Spell Damage
I'm a lvl 31 Master mage. I was testing my new weapon and noticed my spells don't do more damage when using the new weapon.
I'd do about ±5% damage compared to using my old weapon (which is magic wand of life +3). This is consistent when I use the same spell against the exact same monster (not just of the same name). I was expecting a 20% boost in spell damage. Currently, it basically makes no difference.
My last 2 battles, swapping weapons in between:
You hit R3D4-MK3 with Ice Needles for 1267 damage points
You hit R3D4-MK3 with Ice Needles for 1315 damage points
You hit aeroid with Ice Needles for 1296 damage points
You hit aeroid with Ice Needles for 1248 damage points
Lvl: 40
Damage: 392
Value: 750360
Equip Bonus: +20% Spell Damage
I'm a lvl 31 Master mage. I was testing my new weapon and noticed my spells don't do more damage when using the new weapon.
I'd do about ±5% damage compared to using my old weapon (which is magic wand of life +3). This is consistent when I use the same spell against the exact same monster (not just of the same name). I was expecting a 20% boost in spell damage. Currently, it basically makes no difference.
My last 2 battles, swapping weapons in between:
You hit R3D4-MK3 with Ice Needles for 1267 damage points
You hit R3D4-MK3 with Ice Needles for 1315 damage points
You hit aeroid with Ice Needles for 1296 damage points
You hit aeroid with Ice Needles for 1248 damage points