DD-WRT serving additional DNS servers instead of just the router’s IP
It's good that you're using DNSMasq.
You can configure what you want in the Services (> Services) tab, in the DNSMasq > Additional DNSMasq Options box, but first, you'll want to clear those Static DNS fields.
Add the following to the DNSMasq options box:
dhcp-option= option:dns-server, 192.168.10.10 # DHCP option 006
server = 8.8.8.8 # DNSMasq will use these servers for forwarding the DNS requests that it can't serve
server = 8.8.4.4
Info taken from the official DD-WRT site: http://www.dd-wrt.com/wiki/index.php/OpenDNS
It appears you can set the remaining dns servers to non-routable IPs (in my case 10.0.0.0 & 10.0.0.1) and it will squeeze out your ISPs DNS servers with these non-routables. So far for me it seems to be working without any delay waiting on the non-existent DNS servers.
I am not using DDWRT, so this is half-question / half-answer.
The manual DNSMasq as DHCP server says in the section "Extra DNSMasq options" :
There are some extra options in the web interface for DNSMasq that you can set by entering them in Additional DNSMasq Options on the "Services" tab.
If you wish to pass through the DNS servers from your ISP, you can use the following parameters:
dhcp-option=6, x.x.x.x, y.y.y.ywhere x.x.x.x = DNS1 y.y.y.y = DNS2
This seems to mean that passing the ISP servers is optional, so locating and deleting the above line should turn it off.