I completely disagree that Velasquez has slow GNP or that no other heavyweight could have risen from the takedowns as JDS did. Velasquez has used a multitude of GNP strategies during his fights. There is evidence of him trying to remain heavy (a la santos 2, Kongo 1st/2nd round), him opening up (Kongo rd 3, rothwell 1st rd), etc. The man is very intelligent and not overly risky while having a solid finish rate.
I agree with you about the adrenalin dump but it effected both fighters. Both men were much slower after the opening frame. Why santos wasn't opening up was a simple matter of him getting taken down. If he would have unloaded, then Velasquez would have landed in more dominate positions & be able to keep santos down. With santos playing defense, he at least was able to scramble to position he could escape from.
If santos wants to be more effect against Velasquez, he better get in better shape & do more than punch. I would focus on clinch fighting strategies...