I enjoyed raiding during WoW as a tank; at first I thought tanking was going to be too much pressure, too much stuff to focus on and having to be on the ball in a way that requires almost a panopticon view of the rooms; instead you know what's coming and usually WHERE it's coming from, so keeping your senses to these areas is not an issue. Except in raids.
What drove me batty was how super time sensitive some mechanics were; there was a boss in a raid (Halfus wormbreaker for those who've played) who has an attack (shadow nova?) that has a literal 0.25 second cast time that you have to literally hover your finger over the interrupt button to stop him during the fight. IT'S A 0.25 SECOND WINDOW! THAT'S ABSOLUTELY RIDICULOUS!
You also had rotations being so ridiculously important that if you didn't get the rotation just right, you dealt ridiculously reduced damage, and the rotation's importance had to do with stacking debuffs to maximize your damage and keeping the debuff running (rogue). On normal difficulty you didn't need to be this precise, on heroic you absolutely had to pull out all the stops (although honestly even on normal difficulty, unless every player was bringing some dedication we were going to fail anyway).
Then you also had adds that had to be dealt with in a specific order, or had to be interrupted or CCed while focusing on the boss, and bottom line, you had to bring your high tension frenzied DPS rotation to the fore if you wanted to beat the boss.
One thing I enjoyed about the game was that at least normal was doable for the casuals like myself, but heroic really did feel gated off, and that gear from there was just basically going to be unobtainable for folks like myself, and no farming for this currency or that currency was going to give me a longer route to the same items.
I play (played; I stopped playing years ago) this game to have fun, but some of these mechanics (which exist on normal too) and the need to bring your S+ game to the field was ruining the experience; I play to have fun, not to feel like I'm trying to dodge bullets in real life.
I remember asking someone who had played beyond cataclysm classic if raid mechanics got more chill and nope; they got worse.
I'm fine with mechanics that are like 'don't stand in the fire', or 'stop hitting him during this phase', or 'run away during this phase', not YOU HAVE 0.25 SECONDS OCCURRING EVERY MINUTE WHERE WE COULD ALL DIE UNLESS YOU STOP HIM mechanics, or playing whack a mole where if you miss one everyone dies, or where just one or two players messing up meant everyone in the 10 or 25 man raid was going to die.
I play to have fun, not a heart attack.
Apparently mists of pandaria started doing raids where DPS had important roles too that if neglected would also lead to a wipe.
I was curious to try retail cause I keep hearing the raids have gotten ridiculously simple, but I'm honestly expecting my understanding of simple may be wildly different to the average retail player's understanding of simple (so I'm still expecting extremely time sensitive interrupts and having to be an absolute master at your rotation).
Also small note on the aside: I loved DK tanking, it was awesome
You should give Turtle WoW a try, they've added an absolutely huge amount of content to the vanilla client, they did talent reworks on most class specs so that everything is viable, revamped Molten Core mechanics to be more than just something people ignore and will be updating Onyxia / BWL in the next patch along with another new raid and mid level dungeon. Blizzard's lawsuit citing the fucking RICO act will likely be years before there's a resolution and I'll probably be burned out by that point.