Invisibility whenever u want it as a spell, or a limited supply of stealth boys. hmmmmmmm. Illusion wins.
Even stealth boys wouldn't help. Detect life spell remember?

And to make things more fun. Dragonborn casts Undead Thrall on a random dead Deathclaw.
The Deathclaw is now a zombie, and even stronger/tougher.
Yeah but even when flying they don't use that fire breath a lot and when they hover it only goes so far. Not to mention the one thing the Courier has over Dovah is the ability to do a true circle strafe without having to be close to a target. A dragon if it lands it pretty much screwed especially if you see it about to land it would be easy to back off from the range and lob a in nuke at it.
The dragon wouldn't land before it attacked the Courier. Seriously all it takes is one hit, and the Courier is dead.
1. Dragon breaths fire. Courier is dead.
2. Dragon bites him. Courier is dead.
3. Courier runs out of ammo from his constant VATS misses(Vats means [censored] against a flying fast moving enemy). Courier is dead.
No contest.