Here's a quick concept I think would do well...
This is my version of it anyways.. or one variation..
Progression Arena (Uninstanced & Infinite in Player's Joining):
Phase 1 of the first section of the Area:
Defeat Waves of Monsters with 5 Players Max to progress to Phase 2 of the next section
- Once players have progressed to Phase 2, the next 5 players behind them can join Phase 1
Phase 2 of the second section of the Area:
PvP for top 3 utilizing the Arena to deal damage and heal as well as utilizing your own weapons/armour/familiars/etc.
- Beacons activate every 5 to 10 seconds
- bladed-dive/surge/etc towards a beacon to deal damage or heal
- Monsters spawn, kill them turn them against another player
- Once there are 3 players remaining they get teleported to the next section (Phase 3)
- Players in Phase one have to continue with waves of monsters until phase 2 players are done
(Each phase gets more and more difficult to ensure the Arena progresses itself so to speak)
Phase 3 of the third section of the Area:
- Portal Spawning Monsters
- Monsters Spawning from Portals
- Minibosses Spawning Portal Spawners
- Survive long enough to be teleported to Phase 4
Phase 4 PVP
- Top 3 players battle for the top spot
- Deal damage against wave-spawned monsters to turn them against the other players
- Minibosses spawn (turn them against other players)
- Damage from certain monsters increases over time to ensure someone (one) will survive
Phase 5 Boss
- Heal completely.. prayer points, everything by a magical force of some sort
- Yaks come in the arena on the sidelines to provide food (limited supply of heals)
- defeat the Boss, loot the chest to teleport out and rejoin for another round
It's not an elite dungeon in the sense that you'll be in an area taking on waves of monsters before you're able to be teleported to the next area, and that there is PvP involved, uninstanced, and there is actual competition for loot
Added note: There needs to be something competitive and combat related but a quick fix to the combat system just isnt viable, so if the combat system can be translated towards a competitive minigame or PvM challenge into PvP (hence playing the minigame/activity for competitve gameplay), then there could be a solid shot. Personally, the "Silver Bullet" so to speak, would be to integrate a PvP Moba within the MMO (with additional combat systems to out class EOC and enable competition).