I've had my Deco XE75 system for just over a year.  My 2 Decos are connected by ethernet for wired backhaul  I've never really been too concerned with my wifi speeds, since we only use wifi to read emails, forums, and simple internet surfing. Our main PCs/HTPC are wired to the Decos, and I monitor those speeds routinely to make sure I'm getting the speeds I pay for, and I consistently have.

I recently upgraded to 1Gig fiber, and the service came with a Nokia modem and Nokia router.  After the installation, the installer had me do a speed test using the provider's iPhone app to verify I was getting 1Gbps.  I saw wifi speeds of 950Mbps up/down, so I was satisfied.

The next day I disconnected the Nokia router and switched back to the Decos.  My wired speeds remained 950/950, but my wifi speeds dropped to like 50/70!  I tried several speed tests while right next to the main Deco and the results were the same, my wifi speeds were terrible.

Eventually I decided to try using the provider's Nokia router but with the Decos in Access Point mode.   This improved my wifi speeds to 600-700 up/down.

Any ideas why my Decos have such poor wifi performance when used as routers?