Negativity, at least in the sense most mean when cricitising doom metal, has no great purpose whatsoever. It's one thing acknowledging the hardships of the world, it's quite another crawling into the corner of the recording studio and having a little cry about it.
That said, there are a certain few doom bands who surpass (or at one time surpassed) the self-piteous sentimentality which typifies the genre, many of whom (not so) coincidentally incorporate elements from other genres:
Eyes of Ligeia
I remain largely undecided about Thergothon, I think there's something worthy there but I'm never inspired to listen and really try to get something out of them. My Dying Bride's first album is pretty good, too, though very much deathier than the stuff that followed.