Router cpu holding back OpenVPN speeds?

[icece]

Tracing the OS & hardware resources while running different tests shows up a capacity of around 200 mbps for a 2.x OpenVPN client on a AC68U. 50% of the capacity lost with the lack of multicore support. But there's an additional loss of 50% of the result before. This bring me back to my question: what are the deficits of the current OpenVPN implementation?