Nighthawk C7000v2 Extremely Slow Wi-Fi Compared to the Rental Unit It Was Supposed to Replace

So I ordered a C7000v2 a couple of days ago to replace my rental Xfinity Gateway and god I think that was a mistake. The Wi-Fi speeds out of this are abysmal and not at all what is advertised on the box (up to 800mbps on 2.4GHz, 1.9gbps on 5GHz). Before, my devices were able to get 600-700mbps down easily when not even in the same room as the Gateway unit. Now, I am lucky to crack 250mbps on 5GHz sitting inches away from the C7000v2 and 2.4GHz doesn't even touch 70mbps. Wired I still get my 600-700mbps, but the severe drop in Wi-Fi capabilities almost has me wanting to go back to paying a rental fee each month...

Am I missing something huge with this router/modem? How are they able to advertise this as being high speed? This should support well above what my current Xfinity plan provides (600mbps down), yet it has been a major disappointment. Anyone have any suggestions on how to get the full capabilities out of the C7000v2 before I just reach back out to NETGEAR for a refund?