Nowadays, Orshabaal will most likely die in a few seconds because of the high number of players who will be waiting for it. In such cases, the best strategy is try to position yourself around its spawn location and attack it as soon as possible when it appears.
If the server is new, or if there are few players online, you may use the strategy that was for a long time the only way to kill this once-fearsome boss. Lure it to the famous spot near the entrance of Cyclopolis. When it is at red health, shoot Magic Walls so it cannot run away. The blocker should party mode with the shooters and get the loot as soon as possible after killing it. Since it is likely the blocker will not be able to heal quickly enough when Orshabaal performs a strong combo, it is advised to have at least a few mages using Ultimate Healing or Exura Sio on the blocker. A good strategy is luring Orshabaal into a place that you can block only him between 2 trees, or in a corridor where 1-2 Demons limit its movement, helping avoid the line-of-sight attacks. Also its possible to use a medium level char (or a low level) as bait to lure him in a place where he will get trapped by his summons, after that people can easily shoot and Orshabaal will not move until its near death.
Also, keep in mind that when the blocker is blocking Orshabaal, it will still tend to use Great Fireball and Great Energy Beam, so you may want to stand diagonally and far away from it to avoid these attacks or you may experience a quick death.
