Yes, they work great besides the fact the first requistion i got in the hinterlands @lvl 3 was the "Dreaded" Dwarven Puzzle Box. the Obsidian needed to finish the damned thing just happens to be in a Dragon/Dragonling infested hell hole, effectively locking you out of gaining points.
Yes, they seem to generate randomly, which can be very awkward, and I haven't found a way to abandon them in the log-am I missing something.
This, btw, is something I see as a legit complaint with an action item that could be patched. For example, I have the Fereldan locks quest, which it threw me after the hinterlands was almost cleared, and thus, the mobs it says the items drop from-not really in the landscape anymore.
So, seems like they should have been gated somehow. Perhaps allow only those that have mobs active on the landscape to pop, with a randomizing element. And, a mechanism for abandoning the quest entirely to clear the way for a new one.