I think this is a very tricky and important thing to consider. I am not really that big on crafting, but I realize a lot of people are. I'm also not that big on items being the main driver for your characters power, I prefer that to be levels, talents, abilities, what-have-you. I enjoy unique items, and random loot as well. Tricky...
How about something along the lines of "upgrade slots" for items. In these slots, you can fit item abilities/upgrades, etc.
Weapon/armor level = base dmg/protection
Item rarity = number of upgrade slots
Unique placed weapons = unique removable upgrades that has some cool gimmic which retains usability
Upgrades are craftable & findable
Upgrades can be anything from +dmg, +specific spell upgrade/modification, on-hit abilities, etc.
This would make finding new items consistently exciting, because you might find that upgrade mod for that spell you like using. Unique items will be supercool when you find them, but if they don't fit your exact build or your level eclipse their use, you can still break out their signature ability and continue to use it. Crafting will remain a good option regardless of what you find.
With enough types of upgrades, you could keep things interesting forever. Maybe add craftable templates to find/buy, experimentations with different materials to find effects to put into upgrades, merge multiple low-level upgrades for higher levels, etc.
