A couple of things:
In Befallen: Either they've changed the way keys work in Befallen, or they've unlocked the first door for this quest. I can open it without having the key on my cursor (though, I do have that key in my inventory). Also in Befallen: I got all my bone chips without having to go thru the locked door, but YMMV.
In Unrest: Any trash in the yard can pop as a jack-o-lantern, and this includes mobs in the maze. Kill everything except Crabby. Even the one that stands on its own over by the waterfall and the ones in the gazebo. I found the warbone chips drop most in the cellar, but again, YMMV.
In West Karana: Again, anything in or very near to the field, as long as it's not one of the Millers, is potentially a scarecrow. Kill everything except the Millers. And watch out for Tiny Miller- that guy will go after any scarecrows that get too close to him.
In Mistmoore: The Bloody Vampire is NOT static in the graveyard...apparantly, he paths between the graveyard and the throne room of the castle. Or else he just pops in different places. Either way, when I went to MM for trick-or-treat, he was in the graveyard as described. When I went back for the costume bits, he was in the throne room.
In East Commons: Sergeant Ragus does NOT path between Inn 1 and Inn 2. He just wanders the zone. I've seen him near Inn 1, Inn 3 (the hidden inn), Orc 1, and heading to the cave.
On the trick or treat quest: If any of the mobs give you something that's not obviously candy (like pocket lint), then you have to zone out and back in and try again. They guy in Iceclad gave me pocket lint twice in a row.
On the Bloody Vampire quest: Unless I'm very much mistaken, this doesn't actually require a group- I did this last night (using the level 30 shroud method), and he gave me the quest alone. The bone collector quest, however, DOES require a group. Gotta love the consistency.
On the Hungry Halfling: If you want to do this with a minimum of farming, the pumpkin bread and cider each only require one pumpkin flesh. Because flesh drops about twice as often as seeds, you'll probably only need 4 flesh and 2 seeds. To do it with a minimum of tradeskill work, get 5 flesh and make 5 ciders, since those don't require any subcombines.