Upvote for visibility, this is a major issue with using DNS directly to achieve this.
The best solutions I could see (whilst still using dns) was to encourage everyone using steemdns to use a local dns proxy that only forwards the .steem dns requests over the custom server.
Namecoin directions for Acrilic DNS (windows) and polipo (linux) are here https://bitcointalk.org/index.php?topic=205026 - Just swap out references to .bit for .steem and swap IP's for @someguy123's server instead