Is the Bloodstained Letter bugged?

Question

There are, at the time of this question, 209 threads on Battle.net concerning the Bloodstained Letter lore item needed to complete the Primary Sources achievement.

My primary character, a barbarian created on launch day, has been unable to complete this achievement - the Bloodstained Letter simply does not drop, nor as far as I can tell has it ever dropped. It does not appear in my lore list, the achievement is open, and after days of grinding the Keep Depths, continues to elude me. I've never seen the lore - not in Normal, nor Nightmare, nor Hell nor Inferno (where my character currently is).

Blizzard maintains that the Bloodstained Letter is not bugged.

Is it correct that:

1. the Bloodstained Letter should drop from a Dead Solder corpse in The Keep Depths, only on a Dead Soldier (not a Dead Guardsman) and only in the Keep Depths (i.e. not in other dungeons)?
2. the Dead Soldier corpse does not always appear (it's a random occurrence)?
3. the Dead Soldier should always drop the Bloodstained Letter if his corpse appears?

Answer 1

I've been farming Act 3 for keys lately, and the Keep Depths are where I go to build stacks. To answer your questions:

1. Yes. There are lots of dead soldier corpses, and as you noted, the distinction is that the one holding the Bloodstained Letter is a Dead Soldier, not a Dead Guardsmen. I have always found him on the Keep Depths Level 1.
2. I've found it extremely rare that it doesn't drop. My last run had the Dead Solider a couple rooms in. Usually, he's in a little alcove dead-end.
3. I've noticed I get the Bloodstained letter almost every run. Now that I'm paying attention, the Dead Soldier has (so far) dropped the Bloodstained Letter every time.

Answer 2

AFAIK the Bloodstained Letter only appears in the Keep Depths level 1; I also find it almost every time I go through there. Generally I'm anal about searching every dead body though.