I was not expecting Han to survive the Sequels before seeing TFA, given Ford’s desire to have the character die previous. But I thought he contributed to TFA and TROS very well.

For Luke in TLJ, his death had a purpose to the story, it was cleverly and memorably executed, and like ken-obi said above it was likely he would come back as a force ghost for the final film.

With Leia and TROS, I think they did the best they could with the little they had to work with, given the circumstances. I would like to one day see the scenes with Leia and Rose in TROS that did not make it into the final cut of the film.