To do any damage to this brute at all, you'll need a lot of stuff. The Dust is a nice idea. Tie a bag of it to an arrow and make a touch attack to hit it at range with your first arrow of the round. (or use an egg shell arrow) Repeat every 6 rounds as needed if you have enough dust.
You siad they have some resources, so ask the elves for:
A Mighty Oathbow (+4 or higher if possible)
Bracers of Archery
2 x GMW at +5
Empowered Cat's Grace (multiple empowers if you allow that)
Boots of Speed
A spell storing item like a VPP Ioun Stone
A Tenser's Transformation spell in said item
Hunter's Mercy Wand (If the spell is allowed) and a True Strike wand. Since the confirm roll is an attack roll you should be able to use the true strike bonus. (I think you can use these together if hasted...double check the spell descrips to be sure)
Something that can cast Etherial Jaunt for you to either move in after an alpha strike and ambush again (to counter a wind wall or other defensive measures), or to escape if it reacts too quickly. Maybe that broken Ethereal enhancement from DotF. With that, you could maneuver freely after your initial attack. The Dragon couldn't really do much to you after that unless it had Etherealness on it's spell list, but there's still no way to keep him from leaving.
With the above you'll still die screaming if you stay past the first round, but at least you'll be able to do some decent damage if you do.
