Are zones phased in Warlords as well?

[MiRai]

Can many of these phasing issues be from what they are doing to reduce lag or populate areas?

I am on Bleeding Hollow but running around doing Tanaan jungle dailies and I see people from many different servers. Many times I wont even see people when I am flying until I am right on top of them and they just "appear".

Yes, there is a lot of phasing technology in place in Draenor to greatly reduce the load in some areas. This is not the same phasing technology that breaks follow when areas of a zone are different depending on zone/quest progression. I find it to be most apparent when just walking through either of the Ashran hubs (assuming they're nicely populated).