I don't really have a problem with their deaths. Hicks could've probably gone out fighting or some such to lessen the suddenness of it and placate audiences, but at the same time it suits the merciless, apathetic nature of the Alien universe.
When I think about it, though, I'm not sure what keeping them alive would actually add. I mean, they weren't very deep characters to begin with. To me, their arcs had finished, and if anything, Alien 3 just cuts to the chase and gets on with Ripley's story.