I think Sasha fills the void from the Marquis trade to Sactown, so it's more like Murphy and Arroyo (plus cash savings and the pick) for Semih and Gody. The only thing I didn't like, and I still don't like, is parting ways with Semih. I really see backup center potential in him. He's better than advertised, and plays with heart.
For me, it's Arroyo for Gody, and Murphy for Semih. The first one fills the need for a backup PG, the second one fills the need for a big who can contribute in the playoffs. Semih (probably) couldn't do that, although I believe he could shock everyone and play good minutes. Murphy... I hope he'll be a better option, but that's still to be seen.
The problem is DWest and JO are fragile, and Shaq is old, so the Celtics need too many insurance players. But on the other hand, whenever they are healthy, they are high quality players and can be contributors to #18. That's how this roster is built, so I trust them.