Is "wasn't needed" ever a useful metric?Except the final conversation wasn't needed.
In fact, Grey dying at all wasn't needed.
The whole thing could have just as easily been Admiral Tal getting killed instantly in a way that left the symbiot alive, Grey getting seriously wounded by the same thing that killed Tal, and then the symbiot having to go to Adria because Grey's current condition would mean she wouldn't have survived the procedure.
Also, Grey not dying -- or rather, Grey's body not dying -- would be a pretty significant change.