WoW very aggressively resisted informing players about the underlying game mechanics to keep it casual-friendly somehow so players had to test the shit out of mechanics themselves to learn things like aggro values, uncrushability, weapon proc rates, talent behavior, spell damage coefficients, etc. It was a right pain in the ass to get solid info at the time and Blizzard would only give very piecemeal information about how mechanics work. Keeping the playerbase ignorant of the game really didn't help WoW any though.
Also dungeon sets weren't that good for raiding. If you wanted a real set of raid-worthy gear you were getting crafted gear and mix and matching various other dungeon and perhaps PvP items instead of wearing the dungeon set. But a lot of idiots did try to raid in dungeon sets.
They mainly contributed various raid blessings, auras, and perhaps judgements. They were also extremely mana-efficient healers since all their spells had lower cost and crits refunded mana costs. There were also Paladins who tried their hand at tanking, but that went sideways in 1.9 when Seal of Fury got replaced with Righteous Fury. Seal of Fury gave a so-so bonus threat on attack with a Judgement debuff which gave a massive boost to threat when they did holy damage. They did that because they figured Paladins have crap cooldown offensive holy spells anyway, which is true, but if a Paladin went Holy Shield + Blessing of Sanctuary + Retribution Aura + Seal of Righteousness + Consecration with a Judgement of Fury they could generate absolutely unstoppable threat… if you knew the trick, which I think most players didn't, and they still mitigated damage worse than a Warrior. Once Righteous Fury came in Paladins got a rather large threat multiplier on holy damage instead, which made single-target threat a big pain in the ass but they became the best AoE tanks for locking down aggro… assuming you bothered to gear and spec for that while you were still playing healer. Your average Paladin was really just a mana-efficient but poorly scaling healer and buff dispenser.
There were feral offtanks leaning on their absurd armor, but that didn't really go well since they didn't really get shit like defense or uncrushability. Not sure how strong their aggro was either. Druids definitely had a role as the most powerful single-target healers once they got past their mana issues, but they were an amazing failure as a jack of all trades, since cat DPS was a joke, bear tanking was underwhelming, and balance DPS was just weak. They were very good for PvP battlegrounds though.
Oh yeah. Mods were flat-out mandatory for skilled WoW play. And WoW players were incredibly awful unless you had the luck of playing on a seriously hardcore server.
I think "hunter item" was a WoW meme referring to how bad hunter players would try to grab anything and everything.
Blizzard was really garbage about that. They thought keeping the mechanics hidden somehow made the game more casual friendly or shit but if you were playing endgame you had to know that stuff anyway so really they were just being dumbasses fucking shit up for their players.
The real appeal of WoW at the time was the massive amount of people who were playing it, the scenery, and the PvP scene. That was where the game got a lot more fun once you got good at it and developed answers to Rogues ganking you all the time.
Ultima Online was not like that, and it's probably the best MMORPG of all time. I think it also launched the MMORPG genre from the MUDs of yore.