I bought the Archer VR900 out of frustration with routers supplied by my ISPs. However I have noticed my main work PC, which is plugged into the back via cat6e ethernet, is consistently getting slower and laggier internet speed test results than WiFi-connected devices like my phone. In fact if I switch the PC (A 2012 Mac Mini) to Wifi, I get better results.

Now it may well be my Wifi is fast enough not to be a limiting factor in internet speed as I only get ~30/10 Mbit on my ISP anyway, BUT surely a wired connection should a)take precedence b)be at least AS fast as WiFi. 

I've tried swapping cables and so on with no benefit.

As an example right now I get a reported internet speed of 11/6 Mbit over 1Gbit ethernet connection. WiFi reports 26/6 when I switch to WiFi connection on the same machine and re-run the test, with a connection rated at 450Mbit. That's a crazy difference. Can the router really be this bad, or what else could be wrong?

I just plugged an old Windows PC into the router also on ethernet and this gave a similarly bad result.

With the Mac on ethernet, I used iPerf3 to test connection over the network to my phone (WiFi obviously) and get results in the 100-200Mbit range consistently. So the ethernet cable and Mac are certainly cable of half-decent speed which again makes me think the router itself is at issue here.

I'm not an expert in network admin by any means but I am reasonably technically minded. I'd appreciate any help. I put a fair amount of time and money wiring my home office with Cat6 so it's most frustrating I am struggling to access the internet!