Brother, how you run a route depends on the coverage and the route concept. Cooper broke at 10 and rolled to 12. That's completely normal on an intermediate out route. Guys moving that quickly can't make a 90 degree cut on a dime. The ball was under-thrown and lacked zip.
It didn't matter what line he kept there. That throw was going to be under-cut. It wasn't the route. It was the throw.
That play was designed to make the defender choose to either come under the route or go over the pick. Keenum can't make that throw on a play designed like that when you know there's a high likelihood the CB is coming under the pick. You have to put the ball out in front of the WR and over the top. It's an extremely challenging throw. But he's a NFL QB. He has to make it.
I edited that out maybe 10 seconds after I posted it. You quoted my post before I edited it. It was heat of the moment. Which I tried to explain in another edit...but you quoted my post before I could make that edit.