This is a good topic and I think I'm going to echo some of the statements already made here.
First, a tiered system is a must. Why? Without a tiered system, you end up with a system like Dragon Age 2 where a really awesome weapon you got at the beginning of the game is eclipsed by a "Longsword" later in the game and is subsequently eclipsed by another "Longsword" even later. This happened because they had the gear stats ramp up with what part of the game you were in and completely disassociated the naming convention/type of gear from any tier. Not only did this make loot incredibly boring, but very confusing as well. Players should feel like the "progression" in loot is very clear and understandable.
Second, I think having descriptors as you mentioned such as "fine" or "superior" in addition to cultural/material descriptors are fantastic. Even descriptors for magically imbued gear is great. I would avoid the boring +1, +2 stuff. The key is keeping them consistent (i.e. a fine version is always better than a "non-fine") and making sure the art for those items is reflective of the descriptor (dragonscale armor looks like you pulled it off a dragon and made it into armor). So if you kept the variety of base armor types relatively low, but increased the variety of "descriptive" armors within each type, I think you'd create a lot of options for players and player builds. Also, I hate picking up armor that's called masterwork chainmail and it looks like regular chainmail. That's not fun. Whether it's a simple effect you apply to the existing art or new art altogether, picking up that new piece of gear and seeing how it changes your character is one of the key enjoyments of any game.
Third, making armor have some form of natural affinity, either to stealth, dodge, armor, spell casting, or anything else, will be key to allowing you to make trade-offs on various armors and keeping certain armor types viable. For instance, maybe some sub-race of elf is well known for armor that makes the wearer dodge better (simplifying the description, obviously we'd expect you guys to come up with a cooler and more colorful reason) and another boosts your magic resistance. With enchantments being added to the game, players have a lot of flexibility in creating their own jigsaw puzzle of armor type and abilities, so I don't think you guys should feel overly burdened with worrying about whether a barbarian wants to keep wearing a POS hide armor from the beginning of the game. We all know that's just not practical and a player can certainly do that, they should just expect their barbarian to get the crap kicked out of him at higher levels.