Scepter of the Underworld (Wand Damage)

I'm trying to understand why this wand does so much less damage than I expect.

http://www.exiledkingdoms.com/wiki/index.php?title=Scepter_of_the_Underworld

When I compare damage across a range of enemies (which don't show weakness to fire or death), Rod of Incineration always does much more damage.

Is this because Rod of Incineration is pure fire damage and ignores armor class? I'll get something like 17 fire damage from the Rod, while Scepter of the Underworld looks something like this:
23-18=5
6-5=1 (death)

For a total of 6 damage. I have tested this on about 10 different enemy types, none of which are resistant to death or vulnerable to fire.

I am sure I'm missing something very simple here, but I can't understand why the scepter, being a much more difficult weapon to obtain, would seem to be far inferior despite the high mana cost. I don't want to go to Arcanist III if there's no advantage to it in my build.

Thanks in advance!

On what enemy is that damage happening? someone subtracting 5 out of 6 death damage must have a very high death resistance, and to subtract 18 from normal damage it must be a high level monster.

Thanks for the reply! Of course you're right, I must have been testing some against Death resistant enemies (e.g., Vorator) that I didn't think had Death resistance.

I think I'm a little confused on the resistances. So I just tried 3 wands against a Vorator, which according to Wiki has 100 resistance on Death, Fire, and Spirit.

Scepter's second hit log is 6-5=1 (death), which makes sense given the death resistance.
Rod of Incineration is 5-4=1 (fire). Again, makes sense.
But Branch of the Holy tree is 4-1=3 (spirit) which doesn't seem to be aligned given the resistance is the same for all three elements.

I'm not sure what I'm missing here.

In general, I'm thinking the scepter is more specialized than I was originally planning and so will not increase Arcanist to III just yet.

Idk but probably the vorator was having a rough day being used as a test subject for some and his spirit was a bit low but you could try that gain
Now for the answer
Resistance and armor can be a bit trick sot always the same damage is subtracted using same weapon you may inflict 1 damage on first and 7 damage on second 3 damage on 3 given his resistance and your damage applied is not static in most case except jester bow btw i would get arcane 3 just in case if you were in need of the scepter/wand that cost 3 mana to get out of stitaution of specific resistance while conserving mana for an even more difficult situation "it saved me a lot sometimes i barely get out of fight with little to no mana and 1-10 hp"