Man, people really piled on the Mastermind for some reason. What's up with that?
They should all get a non combat ability at level 6. You're getting an extra expertise so it would be fitting. Doesn't even need to be particularly strong, just something to add flavour to the mix.Plus, a lot of subclasses suffer from weak or rarely-applicable level 9 abilities, so once you finally get there, it's pretty underwhelming. The assassin and the mastermind in particular. And on the other hand there's the Phantom who has to wait all the way to 9th level to even get access to their signature ability.