You said is well, whole your post and I can agree with most of it but for me is the issues that people just come here and claim that 70-99% is bad or useless when in their head they are like that because they dont fit on their played characters or top build. Obviously not all items are for eveyone. Some are not so good in PvM but are very useful in PvP for example too. I think it would be fun to go into every category of items and talk about all of them, I am kind of doing something like that here:
Most of items is usable honestly, but I would say like 50% of them could be improved. Some only slightly, some more.
I dont even use stealth most of the time, I dont think its that good. 3 socket breast plate with flawless Rubies is better. Or some uniuq armor and honestly if you look at normal armors, most of them is better than stealth. Maby not for casters, but that fault of people who designed them as it looks like most are good for merc or mele/range builds.
Rhyme is great one I agree on that. There is few good unique shields but you cant find them that early usualy but most importantly its tough to fight rhyme with goiod block and cannot be frozen.
Spirit in sword is overrated little bit, yeah of course its good, but is it bis for sorc for example? No, I often use better Rare orbs I make by using charsi or anya at right level. That goes for playthroughs, if we talk preparing gear for your char, well yeah spirit is usable at lower level and is usable for all casters.
Who mostly use spirit sword? Sorceress right. Well I think razorswitch staff is usualy better but other staves are bad and yes in staves category, most of them is bad for sacrificing shield. I feel like two handed staves was just poor design choice, its like they didnt realize that you will lose everything shield can offer so they need to compensate that.
There is very easy solution to this “spirit” over anything issue. Let act 3 Merc use staves and design new unique sorc class orbs, there are only 3 unique orbs and lowest need lvl 42. I have no clue why they didnt make all orbs with unique versions.
And Lore? Its useful but nothing amazing. Plenty of NM unique helms is better or more useful.
Thats why I am for more mercenary weapon choices and all slots 
Would you keep throwing away all those low level crossbows if Rogue could use it? I would not and giv eit to her as you often find them early. Usage of uniques often goes hand to hand with other design choices in game.
I agree on sets, they are mostly far worse than uniques.
Sorry but you came with pretty bad example Arcaine valor is usable for Immortal ES sorc build. I used it many times in past. But yeah it could be slightly better. General tan do liga and nokozan are normal uniques. Why the hell would anyone use maxroll to design their high level char with them? They are not supposed to be used for that. Nokozan is great amulet for normal where you need fire res, it especially helps against Diablo. General tan do lige? Dude thats one of them most cool weapon on normal for most melee characters.
EDIT: forgot greyform the probably best armor in game you can use on fresh characters and usable for low level pvp? you talk about that one?