Unless hes talking about the rotation the compendium doesn't actually give advice on when to use ravager vs bladestorm, or when to use rend vs trauma for that matter. You have to actually go into logs and do analysis, something which no guide really does. it does offer a link to this "cheat sheet"
https://docs.google.com/spreadsheets...sle=true#gid=0
Its actually a very advanced question, basicly rend+ ravager on almost every fight. There are exceptions for some aoe like Harjatan and Mistress where trauma is good, also on Kiljaeden rend is good but there are a lot of high parses using avatar (personally i prefer it over rend for KJ). Thing is though with your guild comp/strat you might find different talents work better.
Im also going to recommend Corejo's video on what talents and legos to take as well as a basic overview of how to do most fights.
https://youtu.be/rXI1C9iGqn0