DFSUtil is a command line utility that will show you which server(s) a client is being referred to. The command dfsutil /pktinfo is a good one, there are several other switches for this command.
So I have it working in my test lab. I have two servers, svr01 and svr02, both hosting the domain-based namespace, and are located in the same site. I have one folder with two folder targets, one on each server. I have a replication group created to sync the content between both servers.
After connecting to the namespace from my client, in an administrative PowerShell console, I ran dfsutil /pktinfo to view my current referrals. They pointed to svr01. Then, in the DFS Management console, with the namespace selected, I right-clicked on svr02 and chose properties. On the advanced tab, I checked 'Override referral ordering', and selected 'First among all targets'. This option does not take cost (site info) into consideration. (I mistakenly thought all these options used site cost) I then went back to the client, closed all connections, and ran dfsutil /pktflush to clear out any current referrals. Then I reconnected to the namespace. I then ran dfsutil /pktinfo again, and the referrals were pointing to svr02.
Let me know if this works for you,