One thing I have taken for granted in other MMOs but I would like as an option is to dismount when I try to use an ability. For example, I am on my Chocobo flying in Churning Mist. I land and I want to start casting Fire 3 on a mob immediately. Instead I have to dismount manually, then start casting Fire 3 on a mob. It is a few seconds of delay, but like I said, I take it for granted in other games. It could be defaulted to off (you still have to de-mount before casting) but at least have the option would be appreciative. You could also have a second option to not trigger dismounting when actually flying.
Another is more on the theorycrafting side of me. I like to theorycraft stuff and saying "potency of 240" tells me little of the damage to expect. I suspect this isn't a feature for the immediate future, but maybe for an expansion or something, but an "Enhanced tooltip" option that changes the tooltip to show the estimated damage variance of the spell/ability against an at level mob.
IE: "Deals fire damage with a potency of 240." when the option is turned off. With it turned on, "Deals 1200 to 1600 fire damage" against a level 60 mob.