After playing PTR, doing arenas, BGs, and duels.
After playing many different specs.
Here is the spec I will be playing as in 2.3/S3 arena
0/31/30 <--(It's a clicky)
Of course I'm 5/5 mace, but you can switch it to Sword/Dagger/Fist as it fits your weapons.
Although Riposte is going to be very nice in 2.3 with the "No more Immune to Disarm effect" I'd put my points into Ghostly Strike and 5/5 Deadliness.
Hope this helps some rogues out there that need a spec idea for arena.