Are you talking about the one with the planet that only appears in normal space once every so often?Well, that DS9 episode where they meet their descendants from "200 years ago" because in the future the Defiant will be flung there... that could have ended better...
No, it was the one called Children of Time.
I felt bad for the people- even tho I'm sure the end was quick. It showed the depth of Odo's love for Kira.
I mean they technically did exist, they did live out their lives, so I found it sad they couldn't continue... I guess in the big scheme of things it was probably instantaneous and they didn't see it coming... there are worse ways to die. But I felt a little sorry they all disappeared, and it was good of the crew to be at least willing to sacrifice themselves for those thousands of people.
I think with respect you're missing the point. The didn't die quickly. they actually never existed at all.