If the trolls are an issue, Stealth+Bow from a distance. I will take a couple minutes of running away and shooting but the troll wont hit you (if you keep relative distance, the rocks they throw are as easy to dodge as the ones greydwarfs throw.) The 2nd boss will be easy with similar attack way as the trolls (especially if your solo). Other than that, what the others said. Scout, scour, prep- Boss should be the last 'new' thing of that biome.