[Q] Slow Internet Speeds on new ASUS RT-AC88U

So I just purchased an ASUS RT-AC88U to replace my Sky Router (still keeping it as a modem) but I've been having all sorts of issues with it, especially with the WAN speeds I am getting.

Here is my setup :

Sky Hub -- Ethernet --> ASUS RT-AC88U ---- Ethernet ---> 500mbit Powerline

500mbit Powerline --- Ethernet ---> PC

My set-up before was exactly the same, the only difference instead of going via the ASUS router, it was directly from the Sky Hub.

I've noticed that since hooking up my...

[Q] Slow Internet Speeds on new ASUS RT-AC88U