Are you using wifi or wired?
I use TP Powerline 1200 adapters, but the satellite receiver and raspberry are connected to the same adapter. This works also when the second adapter, which is connect to my switch, is turned off. So I think the adapter works like a switch.
When I copy data from my pc over the switch and the 2 powerline adapters I reach about 8MB/s.
It also seams that the channel switch is a lot slower with libreelec (and also Openelec 6.0.3.) than with my old openelec millhouse installation.