To aprogressivist.
About your demonskin cloak, I think that is too many resistances in a single item with not enough vulnerabilities. Also, another powerful cloak already has slashing resistance to it, I'd give it a different power.
Note too that we do not add items with this idea that a "good item" should have an "evil counterpart". It's not the kind of balance we subscribe to. We add items when we feel it will add something to the server, or that it addresses a problem. Granted, it is often to the individual taste and point of view of the Dev adding said item, and tastes varies a lot. But just adding a "powerful evil" cloak to counterbalance a "powerful good cloak" is not our way of doing things. Personally, I seek to add items which adds lore about the demiplane of dread to the server. I will base a good/evil only item, not in comparisons to other items, but based on it's background origin and purpose.
To your comment that "Powerful Evil Only items do suit the server", I disagree. Powerful Cursed items suit the server. Alignment restrictions on items are best avoided as much as possible. A common theme in Ravenloft, after all, is good people slowly turning to evil through the use of an evil item. Staying away of alignment restrictions allows an item to be used by more players and opens up roleplay.