Owned my HTC EVO 3D (rooted, stock rom) for almost half a year already and I have not gotten WiFi Tether working until now based on this post. I’m currently using version 3.9 Beta 9. To get tethering to work, I need to enable MSS clamping and Routing fix under Menu > Settings per this post. Yay! I can now tether when I’m away from home.