I am not using hangouts, but does google show ads in it?
If so have you adblocking of some sorts installed on the router?
I notice long loading times every now and then on my blink feed with my WLAN enabled. If I only use my carrier it loads instantly.
I do have dns based ad blocking with dyn.com. Using my Blackberry as a hotspot I had no issues (its an android tablet). I'll try a factory reset and see if the issue persists if disabling dns filtering doesnt work first.
The issue is that I cannot video call, I can send an instant message but not receive.
The only other thing that has changed apart from FW is I upgraded from adsl to vdsl and have a new vdsl modem but cant see how that would be the cause as t is just a dumb modem, but if all else fails I'll look at that.
had you enabled WMM 'Ack Suppression' aka 'No ACK' on ddwrt? i noticed that it interfered with some things, like SSL, etc. disabling it sorted out problems for me