Tonight I was playing 2v2 with a friend of mine who uses the Arbiter, I mainly play as Forge. Together we devised a strategy that worked extremely well against the people we played.
Basically I, as Forge, would build Cobras and Wolverines, and my buddy, as Arby would make Jackals and Hunters. We found that using this strategy ended up with us having a counter for anything the other team could throw at us. I would use my Cobras to pound enemy bases from a distance which would force them to send their units out. My friend used his Hunters and Jackals to shield my Cobras and kill leaders, infantry, and vehicles. I placed my wolverines in the back in case there were enemy aircraft.
Using this we took out an Anders/Arbiter team, a Cutter/Prophet team, and a Forge/Forge team. The Forge/Forge team gave us some trouble because they kept sending tanks our way but eventually I went heavy on Cobras and we were able to force them back and eventually beat them. This strategy also results in large point totals for both players.
Like any long term strategy it's vulnerable to a rush, but having the Arbiter helps to deter Warthogs and Prophets. Also, since I gather a large amount of boxes I am able to finance a few turrets if scouting reveals a likely rush, as happened in the Cutter/Prophet matchup.
I'm not the best player nor do I pretend to be, feel free to offer constructive criticism of our strategy. Linked below are the games where we used this.
And he's watchin' us all with the eye...