I will start by saying I do not have access to every hidden demon weapon in the game, and was not able to test them all. That being said, I had spoken to others and if other people with different weapons have a differing opinion they are welcome to share. I will share my experiences with mainly the Hidden Demon Staff.
I like niche items and finding use cases for them, but from what I see, current Hidden Demon Weapons are pretty lackluster all around. As we know, the base 5% proc rate is rather low as it is, and the proc results, in my opinion, do not match with the rarity of the weapon.
First, let's talk about the current proc. The website states a proc of 5%, with a drain range of 5-12. This might be more suited for a bug report, but my findings show my Hidden demon staff mana drain range from 1-12. This is not MR based, as I was "lucky" enough to get this range on the same mop.
I have seen multiple procs with 2,3 as well. Yes, as a mage, I feel a weapon with a 5% proc should not be able to return just 1 mana.
Now let's talk about the alternatives. Staff of mana and steel staff of mana have similar damage on paper, but return mana consistently. The hidden demon is more rare, but does include more hit compared to the mana staves, 1 spell power, and 3 mpr.
To be clear, I am not asking for a buff to the damage of hidden demon weapons (although I wouldn't complain if you saw the need for one), but rather the utility of them. And again. this is an issue across all forms of Hidden Demon weaps from my limited experience.
My suggestion for improvement could come in a few forms:
Either a increase in the proc rate, with fixing of the range issue discussed earlier. Perhaps double it and check results.
An increase in proc drain. Maybe change the current from 5-12 to 10-25.
Have the proc scale with int or str, hp draining weapons scale on str, and mp weapons scale on int.
It's not often we get niche weapons that aren't just damage increases, let's make them viable
