I voted for Skilling, even though I am more of a PvMer..
There is just one thing that annoys me.. which is Infernal Axe, Infernal Pickaxe not working like they should and Infernal Harpoon not beeing ingame yet.
I'd enjoy something of a "solo" room for each boss. Id like to do solos on GWD considering its always packed with people on task. I feel like it'd help everyone in the long run.
I would really love to see an extra or an instanced dagannoth cave. It is ridiculous how hard it is to get any rings when you have to compete with others as an ironman who has max gear.