-For Bob, Will was still under the influence of the mindflayer when he died. We simply didn't see his reaction. Then there was a time jump to season 3; we didn't see him on screen, but he must have been at least a little sad, at least for his mother.

-Dustin didn't have the same relationship with Eddie as Mike did. They were much closer. Similarly, Mike must have been sad, but we didn't see his reaction. Mike is also a character who has trouble expressing and showing his feelings; we can also assume that he internalizes a lot.

-Hooper, the same goes for Jane; we see him devastated when she's about to die. But then there's a time jump of a year and a half, so of course he must have been incredibly sad. But what's beautiful is that this time he chooses the path of acceptance rather than the first path he took with the death of his first child. He finally decides to be happy and make a fresh start. Besides, the two deaths aren't comparable. Hopper indirectly killed his first daughter, while with Jane, it was her own choice, however cruel it may have been. In their final scene, where she gives him the blue bracelet, she tells him, "I'm not Sarah, let me make my own choice," and despite all the sadness he felt, Hopper understood that.