Tested on MagicWoW but should work on other popular servers too
Go to NPC Rina Moonspring and get quest A Dire Situation for the quest item Rina's Diminution Powder.
This item will make you very small for 1 minute & you can use it before arena starts as it makes your very hard to target. You can also use it on other people to make them super small in dalaran . This item has 7 charges but you can get it once then mail to alt, abandon quest re-take and repeat for as many you want .
Enjoy ^_^