I'd be happy to get some more details about the Mac client: is it 64-bit? What version of OpenGL are you using? Did you use Xcode for it?
Is the launcher/patcher a Cocoa app?
That last question is odd... why does that part matter?
ESO is 32 bit on mac and windows currently...
Might actually be 64Bit on the new consoles.
The reason the game is 32bit is making a MMO you try and support the largest user base possible.
This means targeting DX 9,10,11, OpenGL.
and making the engine scale as much as possible.
ESO runs all the way back to windows XP, and though that
may not be as a big US user base anymore, it is in places like China.
Possibly because of large scale piracy vs windows 7, or ease of piracy.
On the Mac we use OpenGL 2.1 and Cg + recommended extensions....
Which kind of gets you OpenGL 2.5 as I call it.. or most of the way to shader model 3.0.
The reason we use OpenGL 2.1 and not 3 or 4 was that when we started the Mac version of the game OSX was on 10.6 and we chose Cg as our library to port HLSL to OpenGL.
Now Cg only really recommends ARB shaders as the preferred profile.
Now planning ahead I chose to support 10.7 on up.
That means that in the future we could move to 64bit
and or GL 3.1 etc and not effect the current user base.
Yes I use Xcode for everything.
We use a wonderful open source project called PreMake
which is a very simple to use Lua based project generation system.
It can take files / folders and generate project files or make files for most IDEs.
Since our code base runs across Xcode ( CLANG ), Visual Studio,
Make ( GCC ) this lets everyone code in the IDE and or style they like.
We do not check in project files to source control we simply pull down the current source code and regenerate the projects for our platform.
The patcher is currently licensed 3rd party patching tech
with a CEF / web / CSS front end.