With the release of the DX11 client, the aforementioned performance problems have vanished. Where as before my framerate would dip to the mid 20s or less, no it drops to about ~40 or so. I need to no longer bother adjusting the "Character and Object Quantity" setting to keep a relatively consistent frame rate.

I don't think we'll be seeing anymore complaints about "performance bottlenecks." At least for a while.