I played during the whole Naxx 40 debacle (i think we cleared spider + patchwerk) the issue with the zone wasn't necessarily the difficulty which was a huge kick in the face, it was the number of people who were actually geared to do the zone. there were no catch up mechanics in the game, you couldn't just go quest in the brokenshore for 3 hours and get a full set of 850-880 gear and then lfr and get a working 4 pc, then grab a legendary 970 from a random heroic. you couldn't go to tanaan and be 900ilevel(higher than normal HFC if i remember correctly). We had applicants during Naxx that were still in dungeon gear and we would have to run them through BWL+moltencore to get their 4 pc, then run them through AQ40 for random gear pieces, just so they could join the main raid. this was exacerbated by the fact you needed 40 people who wouldn't "burn out" mid raid tier.
Then if someone got tired of regearing new applicants or just didn't like the way strats were handled they were quickly poached by other top guilds because they were already geared. it led to this giant vacuum where only 1-2 guilds per server could actually have a functioning raid force that was adequately geared. Now i geared up my warlock to 903 ilevel in a week just doing M+ and LFR.
the taunt mechanics were definitely a pain but that was actual game design problems (yay warriors need spellhit now) the actual mechanics of the fights weren't hard, watch a video of any of the fights and there was maybe 1 grouping/spreading mechanic in 90% of them. Kungen likes to rant and rave about " lol naxx was the hardest thing in the world" when it actuality it was just a gear check. I would say take any guild that has cleared Mythic NH or the first few bosses of MToS and they would have no issue in naxx if gear was equatable.
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Mythic KJ is buggy as shit and once again requires crazy class stacking. the phase 2 soaks have to be soaked by DPS with immunities so it leads to people wanting mages/hunters/DH/paladins to stand in shit there are also 2 "tank soaks" in that phase (that the tanks cannot get due to the felclaw debuff). It's also amusing that even with the recent 25% nerf to the damage on Phase2 zones on Mavatar no guild other than exorsus or method have killed it.
I predict we are going to see sweeping difficulty nerfs to a lot of the mythic fights in the near future, probably after the first few M-KJ kills.
On another note i'm really enjoying the sisters fight, we are getting it to sub 50% after about 18-20 pulls and it feels like a fight that is well tuned with a lot going on but is manageable, probably my favorite fight this tier so far.
