Until Ice Block becomes trainable, frost will remain the most effective arena build. That said, the most noticable problem with the tree you linked is its devotion to talents that improve fireball. While fireball is a great PvE spell, its casting time is far too long to be effective against experienced arena players and may often leave you vulnerable while trying to cast it. I would drop the 5 points in Improved Fireball and 4 points in Empowered Fireball in favor of Combustion, Blast Wave, Blazing Speed, Improved Scorch, and the last points in Molten Fury and Improved Fireblast. The arcane aspect of the build seems reasonable, though I would probably not choose the points in Arcane Fortitude and Magic Absorption. To answer your question, if you make these changes the resulting build will be competitive, but may hinder you at the higher end of play due to the resilience that most veteran players have and the natural weakening of the PoM-Pyro combo as a result. I have posted the build below with the noted changes. Hope this helps.
http://www.worldofwarcraft.com/info/classes/mage/talents.html?2300052300230100000000005523201230003125312000000000000000000000000