Honestly anyone involved with current game is likely to see a lot of things in classic they just know need fixing. as far as class/spec's, there are a few that with just a few tweaks could have more utility, but who thinks they will stop there?
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in the context of a forum discussion, I think some posters resign themselves to saying 'no changes' because they well understand that once they get their change the special stamp of approval, everyone else does too. since the entire topic is framed in opinion, there isn't good discussion model for saying well my opinion on the special changes is good and yours is bad because I don't like THOSE changes. so people handle it as if they themselves were personally negotiating the changes, and realizing that any negotiation will be a pork-barrel of changes and an absolute frankenstein of a classic project, they say 'no changes, period.' as the only sane alternative.
The irony is that folks on forums are not the main target market of this game anyhow - it is folks who quit years ago but still play some video games and might try 'classic' given how it will surely promise to not be retail. To this end I expect them (mainly the a/b accessibility ogre) to struggle with a strong temptation to follow the 3.0.2 tuning model. blizzard itself did at one point understand that immediate gratification is a terrible mmo model but it may be that institutional knowledge has been buried in a decade of a/b.