If I'm like 5 feet from the AP I'll see about 600Mbps on 2x2 802.11AC, that's about as good as it's going to get because the link speed is only 866Mbps, and you're never going to get close to that with actual transfer speeds due to overhead.
Speed drops off very rapidly with range on 5GHz, so across the room it'll be down to 300Mbps or so already.
I testing this after reading your comment. A few feet away from one of my APs, I got about 550 down, 650 up. 15 feet away through a single wall, I get 250. I had no idea a 5Ghz signal falls of that quickly.