Imagine a map like the one they use in all the top MOBA games, 5 v 5 Scenario.
First step is selecting your Hero.
To keep it balanced your hero enters the game With a generic set of items that are balanced between the 5 classes.
The starting set is just so you can handle MP0 waves of Creeps/ Monster's. The paragon lvls do not take effect in this area, only lvl 60 characters can enter.
When the Match Starts you will either start with The "Angel's" or with the "Demon's". Just like in the MOBA's there will be 3 lanes, Top, Middle, Bottom, and the Jungle Zone, and instead of Kongor/ Roshan, it would be a random Main Boss's.
Monster's Packs that venture down the lanes will become more powerful as game progress's, just like in the other MOBA's
Gear and Experience will come from Creeps/ Monster's. The only type of gear that drops is ilvl 63 loot, Experience earned in the Game will add to your Paragon leveling after the Match, the winning team will receive 100% of all earned experience and gear and the loser will receive, No Gear but will retain earn't Experience.
The items will not have to be Identified and can be equipped ASAP.
The match's would last on average for about 45mins to 1 hour.
Also After the match you will receive a rank, the rank will be based on weather you win or lose match's ( Similar to League of Legends and Hero's of Newearth ).
This is just a idea for other styles of PvP arena's that could be implemented into the Diablo 3 world, feel free to let me know what you think of the idea