Do you think Hardhome was a trial run for Valyria? That is to say, a Trinity for a Hiroshima, and if so do the Faceless Man/Pate(Jaqen) plan to go three-for-three again?

No. I think that’s completely against the Faceless Men’s code. Remember the Kindly Man rapping Arya’s knuckles for saying she would kill the insurance agent’s guards? You don’t kill people whose death hasn’t been prayed for.