What you're saying may have something to do with the issue for sure. I have ripped out the Intel card - note I am running Windows 8 46bit Samsung T700 - and am running with a Boradcom WiFi / Bluetooth card.
In the registry I looked at both GUIDs. My Broadcom card (that works like a charm) has the following setting:
Value name: DhcpConnForceBroadcastFlag
Value type: REG_DWORD
Value data: 1
Whereas my GUID for the old Intel (still there after removing the card) is set to:
Value name: DhcpConnForceBroadcastFlag
Value type: REG_DWORD
Value data: 0
The very last line in the Microsoft article gives a clue that this setting for Win7 and I suppose Win 8 should be set to '1'
This might explain why the experience is so varied on differing routers. When I turned N off my Cisco and 3COM access point connections were ok (although running on G only) but the TP-Link in work was up and down like a bride's nighty every 30 seconds. This is something to do with polling and DHCP polling well may be it.
Before I fit the card again it would be good to hear if others find this a magic, all dancing, all singing fix?...
C-