I am sure the pogopins are an issue. My Wifi works, poorer is some instances, the same in others as compared to my wife's iPad and my Thunderbolt. But in the instances where the Wifi is worse I can press on the face of the Prime where the pogopin for the Wifi is and speedtest will go from 2+ Mb to 20. So I do think those pogopins are a big part of the problem.
And that happens with the back facing the position of the router.
I'd say so. I put shims under all my antenna and went from 0 sats in view (got 1 one time by pinching, never worked again though) to 13 in view and 9 in use. The .13 update has since turned that into just 1 sat bouncing in and out constantly, not sure why.
I also didn't used to get full WiFi bars even sitting directly underneath my router with a -50 dBm or so. After the shims, I pull -40 dBm and get full reception under my router.
So, yes, at least in a number of Primes the pogopins are making a piss-poor connection and causing some of the WiFi/GPS issues. Not all of them though.