We he is all hyped about Jedi Knight so I think we are stuck with the class.
He did play both a Fury War and a ret Pally in wow and did...ok. I don't think he ever topped the charts on dps but he didn't do badly certainly even on raids he was never too far behind the top guys. I showed him time and again about key-binding but he just isn't willing to change his style of playing if it isn't a huge factor.
Like I said he does well as a clicker..just not the best.
I agree that something like the Watchman spec would be much harder than say a focus spec for clicking.
I don't have a Guardian so I have no clue if the Vig Knight is like the watchman spec or maybe not too much like Watchman.