so, one weird thing I've seen people complain about since WoW classic was announced is the perceived difficulty of vanilla.
people say that since we're no longer noobs we'll steamroll through all the content, thanks to better strats, better addons and better communication everything will be extremely easy
people have also rightly pointed out that a ton of the content has been nerfed after vanilla, elite quests became regular ones, bosses were nerfed etc.
people also claim that raiding will suck because too many speccs are just not optimal, why take a shadow priest over a warlock? why take a boomkin over a mage? etc.
also worth noting that only about 1% of original players even entered naxxramas, let alone beat it
so, in the end, if this time around 4% of players end up beating naxxramas, and one of your 6 tanks is a bear (slightly sub-optimal) and one of your 6 tanks is a pala (quite suboptimal), is that really so bad?