Actually Dicordation thing work more as a reverse of charcter. This is why Discorded Rainbow Dash was unloyal to her friends, Fluttershy was mean as fuck and Doctor stpped caring. So Discorded Discord would actually be a quite nice guy.
The Valeyard is not a future version of the Doctor. He's an alternate version of the Doctor from another timeline. What separates these two Doctors? Well, I have two theories, the latter I agree more with than the former:
-The Valeyard is Zerum
-The Doctor regenerated after Dinky stabbed him in the heart while defending her mother.