Classic demonology warlock questions

i'm prety new to WoW and i started playing a demonology warlock last week. i've been reading guides and watching videos on rotations and whatnot and noticed that everyone always leaves out a lot of their abilities. all of the curses and also fel domination which sounds like it would be really useful. i'm sure there's a reason people leave these out of the rotation but what is that reason? via /r/wow https://ift.tt/9VoYQ7k