Slow Uploads with RT-AC3100

I am on Comcast network and getting great download speeds (130-160 Mbps with Blast Pro) and decent coverage. But with 2.4 or 5 Ghz wireless I cannot get more that 1.5-5 Mbps uploads. I just replaced an old Airport Extreme 802.11n which was getting about 90 down and consistently 10-12 up. I have latest official firmware and have tried disabling QoS etc... to not avail. Anything I can do to address this?

Thanks