I think that an improvement that can be made is the actual game has an announcement made when PTR comes online so that more players are aware that PTR is online. This can really help in improving the number of players on PTR so that more constructive feedback can be provided as PTR games tend to be far less than half full. Full games on PTR will help to evaluate the balance of the game much better than some half witted game of 6 townies and 1 mafia (day 2 rolecall ggwp).
Btw for everyone else reading this, public test realm is currently up, please come and play, and explore the newness of 1.6!