For the Hallow's End quest "Fire Brigade Practice," the scarecrows should be on fire and dousing them with the bucket should count toward quest progress (correct behavior shown in this video from Wowhead). When tested, no fire was present and dousing the area where the fire should be didn't advance the quest. See attached video for current behavior.
This is on the MaNGOS WotLK test server (Covenant, Solar Flare). Only the Dun Morogh version was tested. Quest ID 11439, reported 10/26/2018.