I Just read this
"In addition, polymorph will not give you diminishing returns unless you have to do it at least 4 times (usually due to dispelling)"
Which is quite simply incorrect. I don't know what else to say. This type of thing can rob you of your credibility entirely, and indeed the entire tentonhammer site.
It isn't even a minor mistake. It is glaring evidence that you have zero experience playing a mage in any form of PvP setting let alone arena, yet you have written and posted a "Mage Arena Guide" which will no doubt be read by hundreds of soon to be misinformed mages.
Even though you have never played a mage in PvP, you could still have got away with writing this guide had you done the smallest amount of research at something like wowwiki, where the subject of diminishing returns for various spells including polymorph are well documented.
YOU CAN'T WRITE AN ARENA GUIDE FOR MAGES IF YOU HAVEN'T PLAYED A MAGE IN ARENA.