DHE ciphers are currently supported in an NSS client, the reverse proxy should be able to enable those ciphers.
This can be done separately from any DH support in the server.
Locate the SSL/TLS configuration section in your reverse proxy server's configuration file. Add or modify the cipher suite list to include the desired DHE cipher suites. Each cipher suite is represented by a specific string. For example, if you're using Apache HTTP Server, you can use the SSLCipherSuite directive to specify the cipher suites.
If anything this would be NSSProxyCipherSuite. I forget the reason I opened this but given it's been almost 8 years since I did so and I haven't gotten around to it, I'm going to close this as wontfix.
Metadata Update from @rcritten: - Issue close_status updated to: wontfix - Issue priority set to: None (was: 3) - Issue status updated to: Closed (was: Open)