Diablo – Which monsters explode on death

I started by removing my gear to get best controlled answer possible to make my damage not fluctuate so much. I equipped a low level bow to my demon hunter and went to hell act one. There I started my tests on zombies using my elemental arrow since it does the same damage under different element types due to runes. Against the zombies I use Elemental Arrow with no runes as a basic constant. It dealt around 200-300 damage each shot. I then changed the runes to Frost Arrow and electric Arrow. The outcome was the same 200-300 damage. I decided to test my idea on a more diverse group of enemies. I found some carrions and moon clan, repeated the experiment and had the exact same outcome.

I decided to use test on a creature that I was positive had some type of resistances, Inferno Zombies (which are on fire) in the Halls of Agony level 2 in Act 1. I shot the monsters with Fire and it averaged around 160-250 a shot. Electric averaged 200-300, and frost arrow averaged 200-300. I then decided to try to see how this scaled with gear. I equipped some of my gear and went back in to the area. My Fire arrows were averaging around 1,800 while my frost arrows were averaging around 2,800.

As A final test I decided to go to act 2 and hunt down a construct. I found a Chilling Construct and a Burning Construct and shot basic Elemental Arrow (which is fire damage) and averaged for around 2600 damage on the chilling but 800 on the burning. Swapped to the Frost arrow rune and averaged around 1000 damage on the chilling and 2400 on the burning. Then swapped to the Electric Arrow and averaged around 2500 damage on both constructs.

From the test I have gathered that an enemy has a high resistance to the element that it is, but will not have lower resistances to the opposite elements of its type. Also, an easy way to tell what element type a creature is would be by the type of damage it is dealing (example the Constructs stated above.)

No, Rupture cannot cause a chain reaction.

I just finished testing this, here is the method that I used:

1. Purchase a weapon with a low damage spread (high minimum and low maximum damage). This is important to distinguish between damage caused by Cleave (which does 120% weapon damage) and damage caused by the Rupture explosion (which does 85% weapon damage). If there is too large of a spread, it becomes difficult to tell in the videos which one is which. In this case, Cleave did around 43-47 damage against skeletons and Rupture did 27-31 or so. The weapon I purchased for this is called a Fleet Hulk:
   

2. Run around in the Cathedral for several hours trying to find the ideal group of enemies, taking video and analyzing it for places where Rupture should be spreading but isn't.

3. Upload and annotate the video (Here it is!). If anyone sees anything in the video that makes my conclusion seem incorrect, please let me know and I will try running more tests.

I captured quite a few other segments where Rupture also didn't chain, but in those cases it seemed like there was some doubt since the enemies were a bit more scattered. This video seemed like the most conclusive test since the enemies (especially the group on the right) are quite closely grouped but still don't cause any additional Ruptures despite an enemy dying from Rupture damage right beside them.

Note: In case you're wondering how far 8 yards (the range for Rupture) is in the game, here is a handy image.

Edit: Apparently the annotations got messed up on the Youtube video, I'll try to post a new version when I get a chance.