So I have done the Pit of Heresy 7 times now, each time a different week, and at the end I have gotten a masterworked dreambane cloak as my pinnacle drop each and every time. Every single one of my pinnacles I have gotten has been the same, a masterworked dreambane cloak.
-
As the drops are RNG with no duplicate protection, this can unfortunately happen. It can be the same item each time, or a different item each time or any combination in between.