As stated in the previous posts I would just like to add with some personal experience that hunter is probably one of the best classes to choose for arena.
For the 5v5 arena vid I made recently I did some games, went in without any experience or preparation. Could still easily win many games just because of the synced burst dmg 5 hunters can offer.
If you look in the vid I made you will see its not hard to 1 shot out of stealth, or even later in a game if you do an aimed + chimera, or just chimera and then finish with kill shot.
Hunters also have deterrence which can give you some time to turn around the control of a game by throwing traps and reflecting some spells