These are the addons I use in arena. You definitely don't need all of these and infact I was able to achieve rank 1 using only OmniBar and BigDebuffs. I use more now just to make things easier for me.
I also have an addon that runs a script everytime I log in to change the names of enemy players on their nameplate into numbers coresponding to their arena frame number. Maybe coming soon but I have not hosted it anywhere yet.
Some additional popular addons that you might consider using are: