So, I want to farm the Wizard City Lost Pages Boss, I am Level 5, and want my friend to help me out who is 120, does that ruin my chances of getting the rare drops such as Bone Dragon mount?
It will ruin your friend's chances, though. He will need to fight the boss in Azteca in order to have any hope of getting the mount.
Still. Don't you think having a level 120 slam you through a level 5 dungeon is just a little bit ... wrong? In all honesty, I don't think you'd deserve either the badge or the drops if you just sat there watching while such a high level wizard did all the work.
Let's say you're in first grade and you have your cousin in college do your book report for you. How is that not cheating...? You know that it totally is. What you're suggesting is pretty much the same thing.