GTM persistence with load balancing

More than likely, all clients will be configured to query their local DNS server, which will query the GTM on their behalf. So GTM will see all queries sourcing from the same IP address (or limited set of IP addresses based on the number of LDNS servers in the client's network). In a situation like this, you'd need some local load balancing mechanism (with cookie persistence perhaps) to be able to properly distribute load. Don't think this is going to be accomplished at the DNS level.