but its sad that my RT-AC66U and DIR-655 Sit 6 inches from one another and its sad that on the 2.4 band my brand new top of the line $190 asus cant even match letalone beat the performance of my 4 year old d link worth half as much
Some routers will be more aggressive in "overriding" any interferring router, while others will properly back out if there is already another router using the same channels. If you do have both routers up at the same time at such close proximity, that might be what you are experiencing, where the Asus would back out. Make sure that they don't use overlapping channel.
and as for the dual wan mode im just curious exactly how it works
Dual WAN can work in two modes:
1) Fail-over
In that mode, you have a primary link (the WAN port) and a secondary link )either a specific LAN port, or a USB port). If the router detects it lost connection on the primary WAN, it will start using the secondary WAN for your Internet access.
The current limitation is that once the primary comes back on, the router does not properly detect it, and will still remain on the secondary, until the secondary fails, or the router gets rebooted.
Asus have been notified of this issue.
2) Load-Balancing
In this mode, every NEW connection (important to note the "NEW" specification here) will get spread between both connections, going through an established ratio. FOr instance with a 3:1 ration, it means that the first 3 new connections go on the primary WAN, and the fourth one goes through the secondary WAN.
It's important to keep in mind this applies to new connections only. The load balancing isn't done at a packet level, but at a connection level. That means if you start one single download, it will only use the max speed of whichever connection it's going through. However if you use something like Bittorrent which establishes dozens of connections, they will be spread between both WANs, giving you an effective speed close to the sum of both Internet connection.
load-balancing is usually good if 1) both connections have fairly similar speeds, and 2) you have a lot of users sharing these connections.
There's also been some reports that load-balancing isn't working 100% yet either - I haven't tested that one personally (only failover mode to confirm that the recovery feature was still not working).