Would it ruin the game?

[Torok]

Ok, do I barely got into the main quest, I haven't even met the Greybeards yet . But I have gotten far into Dawnguard. I'm going to retrieve the Elder scroll. But it's the same one that I got for Paarthurnax. Will it be a horrible idea to get the elder scroll this early into the main quest???

 

[Octavia]

Not at all, it just means you'll already have the scroll for when you need it in the main questline.

 

[DrunkenMage]

Just means it'll save you a journey and a half later on.