So a few things to mention through out the post of people saying.
Threat someone mentioned about managing it in vanilla the assumption because of threat run now in retail is the thought that the majority of people who will play classic is from retail with no classic exp. Probably not so much chances are the majority of those who see raiding in classic will be those who played it in vanilla or ps servers so as a player who has been through it you know about how threat is handled in vanilla.
Now to the OP:
1: Yes they are better however in a sense of prepping and skill. Most guild that are looking to go hardcore raiding or even focus on raiding will have there ducks in order before even even going day 1 of raiding. This includes links to videos, diagrams, spreadsheet for BiS, raid composition etc. Knowledge to all the loot tables. Unlike 2005 where you for the most part were learning as you go most of the knowledge is upfront its just executing it. People will be going into these raids gear ready and mechanics on memory.
- Yes and no, No not as many mechanics as some of the today’s current raids but still come with mechanics none the less. In both iterations of the game most if not all mechanics are scripted meaning they will always happen at the same trigger. If said mob does this at 30% health it will always be that way, you will always know at 30% this mechanic is happens and this is how you counter it or react to it.
3: Ya pretty much nothing new is happening with these bosses.
4: again yes and no. You still need 40 people, you still need the right raid composition and the gear to boot these will take come guilds more than other time however you are gonna be hard pressed to find guilds that aren’t gonna go into these raids more than prepared and geared making these raids much easier this next go around. There will defiantly be guilds that hit road blocks but yes there will be some that will steamroll and move to the next.