PvP is an uninspiring waste of time solo. Even with the fixes, largely due to latency issues. The other reason you probably don't feel like you're progressing is because Exotics no longer give a power gain. Even if you didn't get one in the session, you knew you might have, and that small increase in power would drive you to come back. As it stands, since the only way to gear up is milestones, there's no real reason for a solo player to sign in more than to do their milestones.