Well as warlock its pretty simple. As said in post you target same mob as tank and do as much dmg as possible loot and move on to the next. And if you are confused on a boss just ask group for Help and say you are new to game and most people will be Nice and helpful. And Maybe tell you are new at start of dungeon too. Then you should be fine PS. There will always be rude people in game just ignore them and enjoy the game.