Okay - mine is working now too - and I have possible reason - before it was displaying channel 48 as lowest - which is wrong for the AC... I have switched couple of times regulatory domain and it magically fixed. The odd thing is that it is now the same domain I had before (Europe) but now the lowest channel is correct (36)
I'm getting ~185Mbps in "server" mode and ~120Mbps in "client" mode. But watching the router's CPU during that it totally makes sense... iperf is beating on the CPU during the xfers, so... it can't process data any faster.
Makes me think it's a non-optimally-compiled build of iperf perhaps?
Okay - I am still playing with this performance - normally I operate on EUROPE regulatory domain and this leads me to 100 Mbps iperf max on WiFi AC (AC-only, channel set to auto, width set to VHT, extension upper-lower, explicit beamforming)
When reg domain is changed to US I can reach by choosing same settings but channel (161) 150 Mbps - any idea how to configure router to get most of AC in Europe? (when red domain is set to US I am still far from maximum throughput... )
My hardware is D1800H <-> Intel 7260 card
EDIT: After increasing TX Power to 260mW on US reg I get 170 Mbps