Well...here is what you do...Do the GY first. If you can handle that with ease then you know you have the right level. Not being sarcastic when I say that either. GY is your testing point for SM. If your toons cant handle the NPCs on the way in then your probably too low for the instance. For instance, if you cant handle the Hound Master in the Library then you may want to grind a few levels in GY before taking him on. Herod is really easy once you figure out to avoid him when he goes in that spinning mode of his. I once read that SM is really the start of learning how to do other instances. So keep this in mind as your levelling your toons. The Cathedral now woohoo is another matter...again it teaches you future instance runs. Not sure if you need this or not...but the Cath..just cautiously clear each side and center first. Then clear the left corner and then the right corners of all NPCs mobs. Dont let them run back to the boss either lol without clearing all of the NPCs out. Did that once and got wiped really really fast lol.