Since three of these are a progressive armors,
I'm using a "defense" number by placing the armor
on my hero who is dex:18 NM:45 CM:8 with a base
defense of 37
Shadow Leather: def=151 (Progressive Armor)
+2 health regen, +3 mana regen, +2 int, +2 dex
Nightmare Robe: def=151 (Progressive Armor)
+1 health regen, +5 mana regen, +2 int, +2 dex
Natures Vesture: def=184 (Progressive Armor)
+1 health regen, +1 mana regen, +2 int
Ice Cloak: def=77 (NOT progressive, base def=40)
+1 health regen, +1 mana regen, +2 int
shadow leather and nightmare robe are really quite ballanced. Natures Vesture gives a higher defense, but has very inferior regen and ability bonuses. Ice Cloak, not being a progressive armor, really can't compete on pure numbers.
Now, personally, I think health and mana regen are the MOST important bonus you can get in LOH. Nothing else impacts the game quite so strongly. So, on that level, clearly, Natures Vesture, and certainly Ice Cloak, simply can not compete.
However, I still USE all four of these armors, one on each of my parties four mages. Why?
I like my characters to look different. If you just go with the best solution for wizards, you have four party members all wearing shadow leather or nightmare robe and a fedora. BORING. By having four different armors I can tell adara from evangeline at a glance. Even on map view.
Also, Natures Vesture and Ice Cloak just LOOK COOL.
And, most important of all, story. Putting Adara into dark elf armor just doesn't seem right from the story perspective. Natures Vesture fits her quite well. And Evenageline Simply SHOULD be in cloak of ice. I wish I could get the gloves and boots on her, that would make an AWSOME set.
Are my regen bonuses at their max with this arrangment, no, not at all, but story outweighs bonuses in my opinion.