There is nothing known either way, it has nothing to do with my personal opinion. You are stating Dark Trolls lived peacefully and never instigated anything, without a shred of evidence either way.
---------- Post added 2013-02-25 at 05:07 AM ----------
No, they don't have a common ancestor. As written in that magazine, Night Elves come from Dark Trolls, supposedly confirmed by Freya and Cenarius. While this could and should be thrown out in lieu of some lore that isn't one liner crap, for now thats the story. What doesn't have much explanation are Dark Trolls. Nordrassil was planted after the War of the Ancients, the Well has not been confirmed as a source for the change.