Phantom Assassin is a hard carry who relies almost entirely on physical damage to get kills! I played this game with a few friends and our early laning stage wasn't the best, but you should be able to be active in teamfights and help out once you hit level 6 and can start critting for damage. Rely on your dagger and blink combo to give you chances to do crit damage.
This is a Phantom Assassin gameplay that I played a few days ago. Phantom Assassin is a Hard carry who has amazing chasing and Initiating potential. Once she gets a BkB she can easily just blink in with Magic Immunity and have a great time.
Here is my first gameplay of the 3 new heroes! I have a Chaos Knight video recorded which will be uploaded later, and still working on a gyrocopter one. Phantom Assassin is a hard carry who has extreme levels of chase and damage output. She isn't too bad at farming either once she gets her battle fury. She will probably see some experimentation in the Dota 2 Pro scene, so make sure you look for her in some upcoming casts!