The metal rats and chicken came from nowhere, so they threw me a little bit off the game, but in Divinity Original Sin, I think the most boring writing I had to read was the serious one, while I appreciated most of the humorous one.
All the "guardian" stuff was really bland for me, including most animation videos, whereas I really liked the humor in some characters (the prost- no the lady who read books to you, who you rent for the bored troll, the immaculate students touring Luculla, the sketchy fabulous five, the hard hearing mayor of Cyseal, the beast who wants you to kill its goblin master...) and in some zones (the elemental war in hiberheim, the stone wars in Hunter Egde - genius).
Now that I think of it, the rares instances of humor I didn't really liked much were the ones that didn't mesh particulary well with the world. Baardvark mentionned the wishing well (you could remove them and nothing would change much), but there's also a big useless zone in Luculla with the animals you must save from being sent to a slaugtherhouse, and the musicians/bohemian camp (you could remove them aswell without changing anything much). I didn't feel like they were linked to anything really in the world.
So I don't really mind the tone (be it humorous or serious), as long as it meshes well within the world (not just some free humor that hides an area of nothing). Given that humor is hard and that you can't strike 100%, overall I think it was very well handled in Divinity, but I agree with the OP: avoid empty humor, I think humor must complement a solid situation, solid story and solid characters, not be on its own. Jokes must have a setup.
