I had to get some figures from @wolfie180g for this, since Dragon!Dean is in their personal playground.
Let’s see… When Jacob’s a giant, he stands about 122 feet tall (19x his usual 6′5″).
Dragon Dean will end up reaching about 50 feet from the ground to his head. 30 feet tall in the chest (measured like a horse). Wingtip to wingtip, he’ll have a 130 foot wingspan.
So, compared to Jacob, Dean will be quite a bit smaller. He’s more like a wolf compared to the giant.