EDH Scion

I like the idea behind your deck, but I would like to make a couple of suggestions. Other than your arrogant ramp, you're really not doing anything until turn 4, at which point you should be able to play scion. I would throw in a couple of small creatures for blockers early game. Mudbutton torchrunner and perilous myr are a great deterrent as they'll poke back if you're attacked. Alternatively you could use elves or myr for that extra bit of mana and blockers. Also, dragon arch = wonderful, but you're not going to pull it out every game. I'd throw in a quicksilver amulet for a second quick dragon drop and a mosswart bridge as an almost free dragon later on.
Also, you really don't have any instants, sorceries or enchantments. There are several infinite dragon combos that are very easy to pull off. Niv-Mizzet + Curiosity = infinite draw and damage. Hellkite Charger + Bear Umbr + 7 land = infinite attacks. Simple combos like these are game winners! I would even look into putting in some tutors to pull those combos out. And because scion can change into any of your dragons, you just need to enchant him! (and btw crucible of fire is my favourite enchant for dragons)
Those are just a couple of my thoughts. It looks like it could be a really fun deck to play, and I hope some of my suggestions help! :D

hey you should check out my dragon EDH using scion it works perfectly for me and i usually have scion out at around turn 3-4 then 2 turns after that i can win the game through the 21 commander damage. you should try to find a draco and hellkite overlord they're extremely devestating dragons.