And good guys outright won't die period in other shows, and we know this. What tension is there when we know none of the Straw Hats won't make it to the One Piece? Only thing I can conceive of is Luffy dies towards the end and his crew achieves his dream "For Luffy." But would Oda have the balls do something like that? It definitely seems fitting for One Piece, which loves to make blubbering babies of even the most stoic tough guys that watch it.
There's been times where the Dragonballs were disabled or destroyed, limited in doing certain things, and we didn't know that would be gotten around later on. Really, there's plenty of tension, and certain characters have stayed dead. 16 can't come back because he was "just a machine."
Toriyama also told Oda not to kill characters, because it limits you. You better make sure you have no more story to tell with that character as they're alive, and their death has a lot of impact and influences the story going forward, like Hughes, for example.