Quick point on terminology. The place you went(Sastasha) isnt a raid, its a dungeon. I bring this up because the game does have other content that are called raids, so it can get confusing. Almost all dungeons in the game(41 out of 43) use a party of 4, so that means 1 tank 1 healer and 2 DPS. There are other instances where you'll find yourself with 8 players(usually 2 tanks 2 healers and 4 DPS but there are exceptions), and a few where 3 groups of 8 work together towards a common goal. The 8+ man content are the ones called trials and raids.

As a run, Sastasha stands out in a few ways. None of the classes are at anything resembling their normal full power in there because of the level synch of the dungeon. As a result, its hard to do things too well and almost as hard to do too poorly. It seems like a lot to take in all at once, thats why i encourage new people to focus on a couple things at a time until it all feels like 2nd nature. So starting with just getting a feel for the hate meters and how your different abilities cause them to grow is a great next step. Pulling and positioning is another good pair to work on.