Sad, but true: pretty much every single character who visits Samson exhibits one, if not all, of these states of mind when speaking with Samson. They might show up hopeful, but they leave depressed. Over and over.
And they can thank Samson for that. He's the one who really sets the tone of the whole poem, and he is a major Eeyore: "Suffices that to me strength is my bane,/ And proves the source of all my miseries;/ So many, and so huge, that each apart/ Would ask a life to wail" (64-66). Translation? He's so depressed that it would take him lifetimes to complain properly about all his woes.
Sure, the poem ends with Samson appearing to find some kind of inner peace and hope. But he only speaks a few quick lines in this state of mind before exiting permanently. And in light of the fact that this inner peace led him to kill himself and hundreds of others, it makes it hard to see this ending as "hopeful" or "optimistic." What it is, is mysterious, leaving us with more questions than answers about the role of God, Samson's choices, and what our role in all of this is.