The quality of YouTube videos has improved over the last two years, putting greater demands on hardware which probably explains the comment you referenced.
I have a Rev A and it does the exact same thing with high quality YouTube videos. That's just how the original hardware was unfortunately, Rev B was a big improvement. You don't have a lemon - all Rev As are like this (and a prudent person would have suspected this might be the case and have sought benchmarks before making a purchase).
In the end you are going to need to upgrade a compact laptop like the MacBook Air more frequently than a MacBook Pro. Chances are by the time the Rev D comes out your one will be over two years old. Might be a good time to upgrade if money allows. That's certainly my plan (I can deal with not having HQ YouTube for another six months
).