The ending of Swansong is so emotional. You've gotten to know all the characters and Bobby Ewing for so long, and then he dies. And I do love the following season with Bobby dead, people acting a bit more emotional. That sort of stuff is normal when a popular person has passed away suddenly. It jars massively when it's all undone by the dream revelation, with Bobby alive and well and in your face more than ever before. Season 10 DVD has a few good storylines and is the last season to have that proper Dallas feeling, but the hangover from the dream revelation lasts quite a while into Season 10 DVD.
Frankly, I'm surprised more fans don't feel as I do, i.e. that Bobby's death in Swansong was the perfect way for the character to go, and it should never have been undone. Dallas did need to move on to new dynamics.