The Orgrimmar Arena rises the line of sight and challenge mechanics a few notches. The first challenge for any player class is how close to the enemy you are at the beginning.
You are on a elevator the moment you are teleported into the random-generated map: Orgrimmar Arena. After the 60 seconds countdown, the elevator moves upwards to the Orgrimmar Arena. The enemy team is on another elevator that faces yours barely a few yards away. When the gates encasing the elevator come down, it is clobbering time right on the spot.
Rogues here are a danger having such a close range advantage. Casters would have to AOE immediately after the gates come down to avoid getting zapped/garroted by rogues. Warlocks can buff the team with detect invisibility.
Healers are really screwed in this map if everyone synchs to jump them when the gates come down. Be quick and alert.
On to the Line of Sight mechanics. On the back of your elevator is a circle on the ground. Healers are encouraged to step with their backs facing on the edge. Within few seconds, that circle will become a wooden pillar rising mechanically some 10 yards above the ground. A nice spot to keep you safe from melee players. You won’t stay up there for long, but enough to keep you alive a few seconds while healing (yourself or a team player); or DPS casting.
There are two more similar pillars one on each opposite side of map. You can run all the arena and force other players to chase. The second purpose of these unexpected pillars rising off the ground is to cause line of sight. Perfect to get rid of an annoying DPS caster/range player for a few seconds.
The other mechanic in this arena is the two lines that divide the center of the arena. If I were you, I wouldn’t get anywhere near them. Those lines switch on and off a fire. If you are caught when it is ablaze, you will get damage, plus some damage over time. Use it strategically to pull some melee players on it before it switches on. The fire can be used on another strategic way. For example, pull a melee player across the line. A healer will probably have a hard time reaching his teammate if the fire is up.
I know I suck in PvP, so don’t mind that. The video below is to show you the Orgrimmar Arena geography and its Line of Sight and Trap mechanics. Focus on that.