Kill him and make sure to Cut the Tail. Tail and Body Carves both have a chanceMark may have a 4% chance, but when the normal High Rank Dios Quests have 2% for Tail, Body, and Reward chances it easily outweighs Marks chance. G Rank is also better chances than High Rank
Do Sticky Situation, I can usually get 2 or 3 every few runs. I don't need them for anything, I just love fighting Brachydios almost as much as I love fighting Uragaan, easy peazy lemon greazy.
You are not allowed to request a sticky.