All:
I know this is a bit later in the cycle, but just reviewed this thread as I was looking at the settings on my AG300H.
I just updated the firmware to DD-WRT - 17798, which was recommended to fix the DDYN issue and everything seems to be working better now.
Further, I was able to set the TX Power level from the default of 20 to 25 and saw my Signal Levels improve by about 10% throughout my house. Should also note that I have both 2.4 and 5.0 networks running and I increased both of them.
So, maybe this was resolved a bit?