Completed Arena as a Level 52 Imperial Vampire Mage.
Equipment: Archmage Robes, Mage Circlet, Necklace of Peerless Magicka, Ring of Peerless Magicka, plenty of healing and magicka potions.
Skills: Conjure Dremora Lord, Summon Arniel's Shade, Firebolt, Close Wounds, Dragonhide, Ebonyflesh, Hysteria.
Notable Perks in skill tree: Twin Souls, Dark Souls, Master of Mind, Necromage.
Vampire: Illusion Spells 25% more powerfull and character powered by The Lord Stone.

First 6 arena's were easy. I double cast Dremora Lord and ran in circles around the arena while my Dremora's agro'd and killed the undead. The final arena's were more difficult as I died several times until I figured out what to do. Upon entering, I ran behind the pile of rubble to the far right of the arena. I double cast Arniel's Shade, which has an amazing endurance. As Arniel's Shade agro'd the undead, I Firebolted the Skeleton's from a distance. I moved a little away from the rubble and cast Hysteria and the undead ran to the far side of the room. I Firebolted the undead and the Shades killed the rest. I repeated this several times during each arena.

I am cheating, wend in with Vorpal sword(660damage en not enchanted) en al perks full en meself at level 256( learning stone).
Last deur there are no anmies en kan not find the kye to safedoor.

I can't touch type to save my life, so I've gone OP. To balance that I play on Master. My Character is a lvl 55 Warrior, in heavy Stalhrim Armor, with a health absorbing axe, no shield, destruction spell in the left hand. I just kept moving so most of the Deathlord shouts missed me, and killed the bad guys one by one died several times. Changed down to Adept in the last two arena.

In my second run at lvl60, used the same tactics died less, reduced difficulty to Expert. There was no-one home in the final arena! That was dissapointing. However FANTASTIC intense fighting. I'll go back sooner next time.

For my third run I set difficulty on Legendary and crafted a stalhrim mace with the Ebony Blade (Major health absorb) and absorb stamina enchantments. Finished the decimation arena on Legendary after several attempts. In the inferno arena got about half way and changed difficulty to Master. In the Surge arena had to change down to Expert almost right away then there was a glitch and the game would only give me the novice setting, :-(. Tactics were similar, lots of moving around but also keeping someone in front of me to absorb health from. In Cataclysm, once again there was no-one home to fight.

Last time my character gained two levels, this time none. I guess this mod won't do as a fun way to gain levels. I want to get to 80 and meet the Ebony Warrior.

After reading all the below, or above as I type, I thought at first that I had to do the mellee thing. You do not have to do it that way if you do not want to. I love my bow skills, so I decided to use them to the max. So far I made it through the first five levels without any problems. All I used was my bow. Here is my setup. Early on I decided to max my bow skills so I have a Daedric Legendary bow, all legendary light armor using 1. Glass gauntlets of extreme Archery-35% more damage; 2. Glass Helmet of extreme Archery-35% more damage; 3. Necklace of Fortify Archery-34% more damage; 4. Ring of Peerless Archery-40% more damage, all giving me Damage total of 357. Also, early on I found a Nordic dagger of Chaos, I disenchanted it and applied it to my bow. Its stat is 50% chance fire, frost and shock, with 33 points of damage to health, stamina and magica. So far I have not had to use any poison potions, but I have quite a few in reserve for any nasties that want to get near me.
Also, and important Sneak tree is 100, with all points; thank god for Shadow Warrior. Archery tree is 100, except Bullseye; Light Armor 99, not maxed yet. Also have the blessing of the Thief Stone, which incidently aids Archery skills.
Basically my strategy is to sneak around and take them out in sections all the while hiding behind any obstacle and activating my shadow warrior ability constantly. The arenas so far allow for sneaking, so I am making use of those barriers, all the while being aware of everything around me.
I will let you know how I fare through the next 5 levels.
Wish me luck, of is it that I make my own luck?

Sorry I forgot to mention, I am level 80 and I was playing on Adept difficulty. I might try the other ones to see how I fare-Expert, Master or Legendary later on, and I will report on my progress.

I have enchanted armor that has four pieces dedicated to decreasing destruction magic cost by 25%. This leads to all destruction spells costing nothing
Seems that no enemy can stand an endless barrage of fireballs