Maybe try switching off the 5ghz connection and trying the 2.4 ghz on its own. Probably will not make much difference but i did read somewhere that the 2.4 ghz signal gets out further.
I can confirm that the Wifi signal is poor even in the same room as the Router.
Well that's the case in my home and in my Daughters home.
Connected to the ethernet cable I get the full connection, Connected to Wifi on the same computer I get half speed.