When reading threads like this, one could come to think that it's actually "the raiders" who are ruining everything for everyone, including themselves, and should consequently be expelled from the game. If you do this, "the raiders" will "feel obliged" to do that, if you change X, "the raiders" will have to do Y, if you implement whatever, "the raiders" will be butthurt and unhappy because of Gobbledygook. They just seem to have a problem with everything or make a problem out of anything, which makes the solution for all WoW problems very clear: remove raiders from the game and everyone's happy.
ToC - if you liked lore, story, new boss / armor / environments, this place was not for you.
ICC - The introduction of the progressive buff/nerf, was gated, and personally people were pugging first few bosses on 10man before that buff hit. Post buff 10man except maybe putricide/lich king(/sindra too maybe?) was comparable to lfr
BWD/BoT/Tot4W - I liked this, but I didn't like the "final bosses" being nefarian/onyxia/sinestra. Al'akirs raid was tacked on with no reason behind it other than "he is on deathwings side". Lacked continuity or progression, in other words.
Firelands - I really enjoyed firelands, lost of new mechanics and it was ok for a mid-tier. It was only 7 bosses though.
Dragon soul - introduction of LFR.
ICC is often seen in a comparable light to ulduar by some. Reasons above why I feel other tiers may not compete.
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Of course it wouldnt feel as epic because when you do LFR you just brainlessly run through the instances and it has no atmosphere at all.
Thats why i think that LFR shouldnt be able to kill the final boss of an instance... for example garrosh... you see the pumping heart, but cannot reach him, instead you have to do it on flex.
Best of course would be to entirely remove LFR... i mean... are there still people at all who solely play LFR? Why not make the new "normal" (=flex) the difficulty for casuals? Lower the gear requirements a little bit more (because you dont have the gear from lfr anyways).
Ulduar was one of my least favorite raids. Would be just like most of the other LFR instances.