I've played with mastrej a few times when playing with JDuff and Fyg's team during their tryouts and i can't really say a lot that hasn't been expressed. Mastrej's aim is okay, but where she really struck me was positioning/feeding. I got constantly bombed due to our scouts being either dead or returning from their spawnwaves for a quick crit-heal. Seems like a nice person, but I would not say she's mid-high open.
Best of luck to you this season, dude.