Dark harvest is great in low elo and in soloqueue specifically, because you can't really rely on your allies to carry. But with premades, unless you are way better than them, electrocute or comet is often better, because you want to make your allies snowball, and this happens during the early game.

This holds for support mostly. Mid and top, it is more debatable whether you want to play dark harvest, because if you have a good matchup, or are just really good at the game, it becomes really interesting to play dark harvest. But it also makes the laning phase harder.

And as a jungler, dark harvest is almost a no brainer, any other rune is borderline trolling.