When launching MinecraftDev.jar with the following command.

java -Dhttp.proxyHost=[host] -Dhttp.proxyPort=3128 -Dhttps.proxyHost=[host] -Dhttps.proxyPort=3128 -Xmx1024m -jar MinecraftDev.jar

The launcher attempts to the connect to the internet directly while trying to download the minecraft data rather than use the specified proxies. In the old launcher, it would use the specified proxy information.

I've tried exporting the following command as well with the same results.

export _JAVA_OPTIONS='-Dhttp.proxyHost=[host] -Dhttp.proxyPort=3128 -Dhttps.proxyHost=[host] -Dhttps.proxyPort=3128'

This is probably a relatively low impact bug, but impacts users who prefer to not have a default route to the internet and force all traffic through a proxy.