Huh....
Believe it or not, due to being grandfathered into unlimited 4G LTE data with Verizon (and them trying every way to Sunday to screw me out of it), since March I've not had a direct line (no cable internet/DSL/etc), relying solely on my 4G via WiFi tethering. This is what I'm using right now, it's what I use to play games including BF3, it's what I use for d/l-ing music/movies, etc etc. With a Belkin small little WiFi-N600 USB adapter (seriously small), and my phone sitting next to me, about 4 feet from the PC....
I get (min-to-max)
25.2-47.8Mb/sec Download
11.1-27.7Mb/sec Upload
9-22ms Ping
Averages are:
39.5Mb/sec Down
24.2Mb/sec Up
11ms Ping
In fact, I am usually in the top 3 if not the number one lowest latency player in any BF3 match, all of which are 64player (I only play on NA servers).
So, wireless works just fine for gaming, I can say that much. The problem is somewhere with the specific equipment.