Invul is what people would use mate. Sell anything else to an npc.
Why not fortification, or other tiers? What is the equivalent level of magic armour to GM crafted armour on this server?
People will buy fort but honestly its just not worth the time and effort. You can vendor them for a few hundred gold less than what people will pay for it and you dont have any of the headaches of sorting, putting it on a vendor, then paying fee's while it sells.