Currently there is no possibility of changing the traffic class in HTTPCore, this could be fixed by exposing the methods setTrafficClass(int) and getTrafficClass() in http://docs.oracle.com/javase/7/docs/api/java/net/Socket.html. This can already be done with setSocketTimeout(int), and there is also a feature request for doing it with setTcpNoDelay() and setSocketKeepalive() (https://issues.apache.org/jira/browse/HTTPCORE-288).
Supporting traffic class could be quite beneficial for HTTPComponents as it allows projects depending on HC to control the quality of service. This could be used by e.g. Apache Synapse to give outgoing request or replies different QoS parameters depending on the client connecting to the service.
As I'm not familiar enough with HTTPCore I can't give a precise suggestion here, but just by guessing the same issues put forward by this issue: https://issues.apache.org/jira/browse/HTTPCORE-288 might effect this request to.