What's the connection speed showing on local area connection? Try chipmaker's driver here. http://www.realtek.com.tw/products/productsView.aspx?Langid=1&PFid=4&Level=5&Conn=4&ProdID=10

No lights at all? What's the problem indeed?

Report your problem here. :) http://ticket.tp-link.com/index.php?/Tickets/Submit

When Wi-Fi connection lost, what's the status, disconnected, limited, connected but no internet? Any IP address obtained? Wi-Fi connection comes back automatically? If you forget the network and...

Your Wi-Fi network is still visible on those apple devices? Tried to connect but failed? Any error message? Try to forget the network and reconnect. Do you need to type in Wi-Fi password?

Try to disable UPnP on web interface of D7. Other wireless clients have no disconnection issue even under high load?