It’s hard to make an objective discussion when people have invested so much time, the average player, especially here on the forums has spent 10+ playing one version of the game (of course not for classic has not been out for 5 years yet).
This is good because players don’t have to be objective, that the job of the designer that have to study and research what works and what does not.
With my short professional experience, I found thing in retail that are great: Evoker, Dragon Riding, but other minor ones I found them an horrible design.
Like many I am playing remix, taking the occasion to level up some allied races I decided to make a Lightforged Dranei Paladin.
With big surprise I found out that Paladin now have a combat res (nice addition), last evening I joined a Mogu Shan normal, shortly after the start 2 players died, in the raid we were 2 paladin, 1 lock and 1 Druid so in total 4 combat res.
But because they decided in Cata that you can have only 1 rez in combat in fight we could only rez one.
This made me realize how horrendous this decision is, combat rez have already a long CD by themself, make them limited his just bad design, because raiding is a cooperative gameplay, all this changes to make it more e-sport like and homogenized for everyone is only making raiding less appealing to people. This is what I believe works better in classic where you have more choice and option.
Take potions for example, on vanilla and TBC they all share a 2 min CD with no limit, meaning that based on the encounter and the situation you can choose if using a healt, mana, combat or other type without all the limits present on retail.