I think the speed of the decision can be framed as a positive or a negative. That is, the QB has to react quickly...but he has less to react to, as the read man has less time to play games. Once the QB understands the basic teaching points, it's not really that difficult to "see the read, be the read."
And to be honest with you, Vad's option % wasn't terrible. He had bad games, just like Tevin did (Miami 2011 being one of his worst) but, on the whole, Vad was about average with the basic read percentage. Where Vad was sub-mediocre in 2013 was what happened in the next phase of the option. He very rarely attacked the pitch read, did not stay on his track, did not run aggressively after securing a "keep" read from the OLB, etc. I think that was evident to most fans - he just wasn't running with the ball the way he needed to
After rewatching some of the games, my take is similar. My impression is that Vad did fine with the dive key when relaxed but ...