I currently run the Focus spec on my Guardian. I cant say I am the best player, but on the same note I never hear about anyone playing the spec. Personally, I feel that the guide linked is a good starting place. Once you feel comfortable with the rotation set forward there start tinkering with it a bit and figure out what works for you. I personally hit Concentrated slice almost on CD. It can hit for over 13k and normally crits if you have your character built correctly. As it pertains to gearing I would recommend currently following the guidelines for the Vigilance spec as no one has put any updated information for Focus. Just keep in mind it is not considered a high DPS spec. But I just hit 5k DPS in HM EV tonight. I was stoked. I was not able to maintain it for the whole fight. But even 20 seconds was surprising. Just keep on keeping on with it. It is good and has high survivability when soloing because it is a single target focus. (Please if your going to correct me on anything anyone, just don't be rude about it).
Also. Crit is the flavor of the month not power.