Basically yeah...

The Rune Axe doesn't have charges exactly, it's power scales up based on the number of undead killed per day (supposedly)...

When I last checked the UESP said that it takes 10 kills to charge up the weapon...

It really didn't feel that way for me during gameplay, it seemed to get stronger and stronger upto about 100 kills and then stopped gaining strength...

It 'felt' like the weapon gained 1pt of sun damage for every undead enemy killed and then capped at 100 damage.

I'd be happy to be put right by anyone who has done their own work with the Rune Axe.

The wikia have updated the page since I was last on, looks like I was accurate...

No! I was really hoping that would work during testing but it doesn't seem to respond to any alchemy...

...a weakness to magic poison may have worked but all undead are immune to poison so that went out the window as well.

I made the decision not to present this character as a vampire, although many of his spells and alchemy would have benefited hugely, I just felt it wouldn't appeal to as many people.

Vampirism is definitely an option if you enjoy it...

This character WAS my only Dragonborn playthrough (that's how I learnt that Miraak was very vulnerable to the Rune Axe), so yes it's definitely good for the DLC.

Ha! That's not what I meant...

I confirm nothing...