Monsters drop no loot when killed by poison after changing instances

I was trying to kill the chaos firestorm leaper boss in a Tora den quest when the boss got possessed by a tormented cannibal so I got scared and left the area. A few moments later I went back in and the boss died to poison as soon as I entered (I'm playing a poison bladefall/bear trapper with Bino's) and dropped no loot: http://i.imgur.com/rd3cbHy.jpg (he's right next to me in the screenshot)

I was able to reproduce this with Voll on merciless dried lake by poisoning him and then portaling out and coming back in: http://i.imgur.com/sGj7gDA.jpg

I disabled my itemfilter in the screenshots to make it more clear. Also I was able to do it with Voll without Bino's equipped.

Yea that seemed possible so I went to test it a bit more. I was able to re-enter the insance and see that Voll still had some life left before he died and I still got no loot:
Before death: http://i.imgur.com/MbQtKSN.jpg
After: http://i.imgur.com/LconrAK.jpg

I'm pretty sure the destiny leather was already there, I just forgot to disable my filter before the first screenshot.

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Because if he actually died while you were out of the instance you're not meant to get any loot.

Just to get this clear - this is on purpose and not a bug?

Because it just happened to me, when I went out of my Piety (Shrine Map) fight to put on Culling Strike and Item Rarity and reentered the map I also did only see Piety dying in front of me but no loot drop at all (yes - she was poisoned when I left).

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BVB_1909 wrote:

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Because if he actually died while you were out of the instance you're not meant to get any loot.

Just to get this clear - this is on purpose and not a bug?

If you are not in the instance when the killing blow is landed then you will no receive credit for it, it's not a bug.

At best, the bug here is that the game played the death animation upon re entering the instance as the boss was already dead

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lagwin1980 wrote:

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BVB_1909 wrote:

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Because if he actually died while you were out of the instance you're not meant to get any loot.

Just to get this clear - this is on purpose and not a bug?

If you are not in the instance when the killing blow is landed then you will no receive credit for it, it's not a bug.

At best, the bug here is that the game played the death animation upon re entering the instance as the boss was already dead

Thanks lagwin for the answer - regarding party play it's kind of obvious that only the players in the zone should be rewarded for the kill... as a solo-player it's kind of weird not to receive any reward, because it was clearly me who killed the map boss (who else...?) But good to know anyway!

One follow-up question regarding poison: What exactly is "the killing blow" when playing with poison?
In detail: If I hit the mob, it gets poisoned, I leave and while I'm out of the instance it degenerates to death, have I delivered the killing blow (and loot drops) or is the poison itself the killing blow that killed the mob, while I was away - thus no reward for me.
In my specific situation I'm not sure if only the poison did damage to Piety after I zoned out or if there were some sparks flying around which delivered the killing blow after me portaling.

Finally - I hope it's ok to ask one more question here, even though it's a bit away from the topic: When I hit a boss with lots of "voltaxic sparks" (with Poison) and shortly before it dies I link an item rarity gem to my sparks and get one or two final casts out before the mob dies, does this garantuee, that the item rarity works on it, or could an older poison stack (without extra rarity) be responsible for the kill and I should use a culling strike with item rarity to force the matter?

Thx in advance, cheers!