I just install my 6416A into dd-wrt and get no problem at all.tested using firmware r27805 for tplink_tl-wr710nv1. And upgrade via failsafe
the firmware link use this “ftp://ftp.dd-wrt.com/betas/2015/09-11-2015-r27805/tplink_tl-wr710nv1/factory-to-ddwrt.bin” . and return to gl-openwrt with no problem using gl .2.0 firmware.