When I actually have gotten into raiding, it was TBC, which still had many weird leftovers from vanilla. Often it was a struggle to recruit people, more so than with bosses, because that needed holy paladin disappeared and we needrf exactly this class and spec. It was more often about "bring class, not a player", had even to decline some better players because we had enough of "x" class. It was one of good things, when compositions became more flexible.
The main topic for Classic at the moment would be whether the game is actually harder or just has more redundant activities you have to do before doing the stuff that's really fun. This is actually a good discussion to have, and not just for WoW, but gaming in general. The main sticking point for now, as most people are on (relatively) low levels is the breaks between killing mobs, especially for mana users. In the beginning it's actually refreshing having to think about what you can and can't pull, not just running into a bunch of mobs and killing them in *insert current optimal time to kill Blizzard determined is the most fun*. The food/drink breaks after a few (or even one) mobs provide time to actually look around the scenery and the mobs you're facing, and while there isn't much strategy involved at these levels, you still at least pretend to plan out how you're going to get to that quest mob without being killed by the 4 random ones surrounding them. Not being able to pull whatever mob you want, and actually having to check what mobs are there when you don't have interrupts yet (casters tend to be a nightmare) is definitely more difficult in a real way than what we have today. As a caster, having to actually think about which spells to use based on mana cost (and perhaps even using lower ranked ones) is definitely more difficult and requires more engagement with your character than we have in modern WoW.

This is another one that will most likely be a boon rather than a bane to the player base, though time will tell just how 14years of experience will affect the economy of Classic WoW. There has been no concrete word on just how AddOns will work in Classic, but if the infrastructure of the game works the same as it does in retail, there is a good chance that most of the mods that work in retail will work in Classic. This means that quite a few people will be running around with a whole host of gathering, crafting, auctioning, and gold making mods. Now, those mods did exist back in Vanilla, but not in the same way they do now, and not as many people had them back then as will in Classic. This will drastically affect how effective the auction house will be, and hopefully will affect the economy as a whole in a positive way. Another thing that will most likely see a large increase in popularity is carry runs. These have steadily grown in popularity since Vanilla, and rest assured with the old 40 man raid size that there will be quite a few “Molten Core full carry master loot ON PST for prices GOLD ONLY” being spammed in trade chat. Whether tokens will be available in Classic has yet to be discussed, but if so it will have an enormous impact on the economy of Classic. This, in addition to the differences I will cover in the next section, will have a pretty large impact on the endgame of WoW Classic.

Other decisions were slightly less clear cut. At one point in WoW’s history, there was an 8 debuff limit on any one target. This was later raised to 16, and today there is no debuff limit. Thes change radically changed the balance of classes and strategies players could employ when using these debuffs to overcome content. To preserve that balance—and to avoid the slippery slope of retuning patch 1.12 data to compensate for such modern-era changes—we’re looking at setting a debuff limit of 16 for WoW Classic.
Classic WoW is the highly anticipated, upcoming (re) release of the original, first World of Warcraft version, known as Classic and by it's other popular ice-cream like name: Vanilla WoW. Dubbed Retail Classic, or Official Classic by the playerbase - it was finally announced by Blizzard in November 2017, after a lot of pressure from the Private Server World of Warcraft community, since the latter's shutdown of the most popular Private Server called Nostalrius which featured the first WoW version in two separate PvP and PvE servers.