Accuracy caps at 100%, so anything beyond that point is wasted. It varies by encounter, but you will almost always be at/near cap until you start to try top content.

Weapon damage is the biggest damage factor by far, higher ilvl of weapons leads to higher weapon damage. Next is DEX, dungeon gear and HQ crafted gear of the same ilvl will have the same DEX. After those you want crit hit, then determination, and way down the list is skill speed.