About the 2 Shards and 1 chunk of Faintstone, and the rest of the loot that spawn in the Leechmonger's area:
I noticed that there were only one or two corpses there after killing the boss (tendency was white, not pure). The only thing I had done different was that I skipped past most of the enemies in the level (took both shortcuts). So I backtracked and killed everyone (without going by the nexus), even sniped the two above the Istarelle ladder location, and went back to the boss area. Now all the loot was back; a giant club, crescent grass, 2 shards and 1 chunk of faintstone.
Just replayed the level on the next game cycle. Killed all enemies, especially all 'sleeping' and hiding enemies, even picked up the Istarelle (was pwwt). After beating Leechmonger there were 2 shards of faint, 1 chunk of faint, a giant club, and a bunch of crescent grass. I believe the shards of suckerstone are there regardless.
Replayed the level on another playthrough. Killed all enemies, but this time a lot of the loot was missing in the boss area, so I went backwards through the level and pushed a lot of the corpses into the valley. When I walked back down to the boss area all the missing loot had appeared there.
One more run through. This time I avoided the area with the crystal lizard and the enemies there. After I took out Leechmonger only a few items were scattered around, so I backtracked and pushed the dead enemies into the valley. When I got back to the boss area the giant club and the chunk of faintstone was there.
So it looks like it's dependent on how many enemies fall into the valley, not what kind of enemies.
I rushed through the level today, and after killing Leechmonger there were no corpses there, apart from the one with 2x shards of suckerstone. So I used the opportunity to backtrack and push 1 corpse into the valley, then back to the boss area to see what appeared, and so on… (some of the killed enemies had vanished when I backtracked from the boss area the second time, so that may have messed with the result)
|corpses pushed into valley||1||2||3||4||5||6|
|appeared in boss area||2 corpses||+1 corpse||+3 corpses||+2 corpses||+1 corpse||+1 corpse|
|available loot||2x crescent
|5x crescent||2x crescent
2x shards of faint
1x chunk of faint
|5x crescent||1x great club|
10 total + the one with suckerstone.