So before Dragonborn came out for PC, Boss Balrog saw fit to spoil that Ysgramor was a dragonpriest based on content from Dragonborn. I haven't found it anywhere. Has anyone else?

Nothing from Dragonborn suggests Ysgramor is. His shield and tomb give enough evidence on their own anyways.

What about his tomb screamed dragonpriest? His shield had a dragon's face on it, sure, but Ysgramor didn't wear dragonpriest robes and he didn't cast magic.

One of the new books talks about how a Dragonpriest gave all kinds super powerful enchanted weapons and armor to Ysgramor.

Ysgramor was not a dragon priest, although, he was part of the Dragon Cult.

The dragon priest inscription behind his tomb. If he wasn't a priest himself, he was connected somehow. Just like every Ancient Nord.