In my understanding for your last example you've got

70%(max chance) One of the two reflects proc

Then there is
1%-20% the two reflections synergize [each time 70%(max) drops closer to your 50%(min)]
meaning each reflection source works separately and sometimes chances collide.

 In the end that should be about a 10% average of 150% damage reflection

Edit: There is another possibility that chances are additive and over 100% start to to merge(a bit unlikely)

But also highly possible and logical considering how TQ works is to work per armor piece being hit
So torso,helmet,gloves,boots have separate chance to receive each hit or shield when block. So chances to reflect are local to every piece (cant recall weapons having reflection or set bonuses)
Skills like Storm's Energy shield reflection should be global in this case

 Normally everything equipped drops when an enemy dies. I've noticed that sometimes weapons don't drop


So this troll is taking that Mjolnir(?) with him in the afterlife 

Is this a common issue?