I've felt that a 95% gather rate is the best XP. I go to the nodes that gives 10% bonus, 5% HQ chance bonus, and extra attempts ONLY. I use the ability that gives 5% bonus to gathering on the two nodes that don't have the gathering bonus. So I'm gathering the highest level item which I can always have a 100% chance - using about the amount of GP I recover as I run from one to the next....