I cannot confirm if this method is more or less secure, however my initial concern with the above method is that there is no validation of the token by domain_client. Without validation of this token, anything could be passed to domain_client and it would pass it straight to your web service at domain_master - this could lead to problems as it could provide an attack vector.
You could implement HMAC for validation of the token - http://www.piotrwalat.net/hmac-authentication-in-asp-net-web-api/
Hope this helps!