Respectfully, I think that you have a prejudice against what you call "counter-punchers." You haven't explained why they tend to be "over-valued" as having variety. Also, you act as if Wawrinka hitting the cover off the ball is some kind of compensation for "variety." Yes, he hits the ball really hard. So does del Potro. Is this really a "variety?"
I have prejudice against Murray.
Off course that a counter puncher can have a lot of variety, but all of them will always seem to have it more than the others, because they are constantly being forced to use shots that would not use if they were in control of the point. Ok, if they are good counter punchers, they need to be at least ok in most shots. But a lot of players are, it is just that being more in control of points (even if they end up making an UFE), you have the choice of using the shot you are more comfortable with. In the end the shot selection is dictated by (the power of) choice.
I am not saying that Wawrinka or del Potro have "great" variety, just that the difference to a guy like Murray is not that big. Hard hitters can have some variety, as they can hit big from both wings, from different directions and with different angles -- even with different spins. Of course a lot of them will mostly close their eyes and hit a monster cross court. But this is not the case with both guy mentioned here. Wawrinka can do a lot of different things with his back hand, while del Po's forehand when is on is not only about power. He sometimes hit it with some odd outside spin which is pretty interesting.
About Murray, ok, he has variety to some degree. He has an extremely good lob as I already mentioned. His drop shot just got better (so that's a new dimension). A good slice (but he uses mostly as a defensive weapon). That's an OK variety. Really not in another league in comparison to del Potro.