I imagine what veterans really look for, at least in non-QB positions are intangibles. They've seen enough busts to know athleticism and talent isn't what separates them from the rookies. I'm sure a lot would have spotted LoRax as one of them dudes that would stick around.
QB's are probably much more simple, I'm sure they know the right zip on the ball when they see it.. after that they just need to see progress not perfection. I remember seeing DeAndre Hopkins visibly impressed with Murray finding him on one play last week.
I think what (good) GM's have been catching up on recently is taking the pulse of the locker room. And what makes Beane and McDermott work as well as they do is their teamwork.
It also helps that new quarterbacks seem to be as good as they've ever been. Before that the NFL had quite a serious quarterback lull for like a 10 year stretch.