So, Sha has a two hour spawn time and has four different spawn spots.
Here's the map Sha of Anger - NPC - World of Warcraft
But, that's not the point. The point is Sha spawns at mentioned locations anticlockwise. By this I mean it.
But, the mechanism doesn't count the spot a little more west of One Keg.
It means, your full raid can actually gather up at a specified spot and get more chances of pulling Sha.
Best regards,
Meice.