Neonchameleon
Legend
Playtest packet 6 lets you take two weapon masteries you have proficiency with - and daggers are one explicitly suggested option.The problem i see is they opted to fix Two Weapon Fighting via Nick, and not giving that to rogues really messes up the action economy again.
Edit: Misinterpreted. But the real reason rogues should get weapon masteries isn't that IMO. It's that having Vex moves Rogues from a class that needs to work to do their baseline damage to a class that should be overwhelmingly likely to do their baseline damage and can then do other things.