The dragon has some odd dialogue when it dies. It's the first dragon you fight

He says

"Dovakin. No."

The problem is I feel this piece of dialogue is a bit to open to inerpretation. Does he mean, No the Dovakin has risen? Or does he mean no dovakin do not kill the dragons?

Dovahkiin*

Yes, I'm sure his dialogue was referring to the appearance of a Dragonborn.

*Alduin returns*

Yay! I can now leave my hiding spot and have fun! Cuz if I get defeated, Alduin can revive me! Woooho!!!!

*all-he-can-eat buffet in Whiterun hold*

Muahahaahahahahaaaaaaa

*Gets defeated*

No biggie! Alduin will resurrect me! LOLOLOLOL stupid mortals!

*Dragonborn lands the killing blow, troll face*

Wait... Dovahkiin??? [censored]!!!! NO!!!!

I don't think it's relevant who lands the killing blow. So long as the Dovahkiin is there, they are done for.

What I don't get is how he didn't know what he was up against from the get go. Paarthurnax and Alduin both seem to pick up on you being Dragonborn, so why didn't he?

Also, I wonder when the Dragons realized something was different about Miraak. Was it the moment he was born, or did it only become apparent to them when he absorbed his first Dragon soul?

Because they can't. Only Alduin and Parthy can because they are Divine. As for Miraak, it was the same time he discovered he had an extra gift. Not unlike his mirror in the 4th era, wink wink.

I know that. Quit killing my jokes you!