I dont know about the correct chest. I only ran 2 legendary run on the middle n right. On both occasion, in both runs, the 1st chest i kill drop gold, the 2nd drop event items. If anyone can clarify the full content of the drop in that chest wave would be great. The unrefined gem i get from the 2nd kill is 16.The chest that goblin took is the "correct" chest that contains many event items and unrefined gem.One took one of my chest, the other chests explode.
If the goblin took it you will only get few event item from killing the boss, without the unrefined gem, making legendary drops worse than heroic drop(in the case you can clear all treasure box in heroic).
I m still new to this game and this forum, but I happen to notice something when my game shuts down and I need to reopen the game and the game asked me if I wanna resume the battle. and then somehow I noticed a glitch which I have been making use of it while I was doing my gold quest.
now, whenever u enter a battle the system will assigned what will be dropped when u kill the specific monster.
for example, 8 unrefined gems and 2 dolls IF u kill the designated chest, and this is fixed once u enter a battle. there's a lot of people saying is difficult to burst the right chest if u probably only have enough fire power to burst one and u would like to be the right one for the unrefined gems, so what u do is at the chest stage focus your fire on one particular chest, if u happen to get the right one then just continue with the boss stage, BUT if the chest that u pop gives u only gold, what u can do now is just wait for the infernal gates and see which chest is the hobo taking away and u will know which is the right one. simply shuts down the game and reopen it and at the title screen u will be asked if u wanna resumed your battle, go ahead and now u know exactly which chest to pop!!!
hope this help and hopefully I don't trigger the alarm for them to fix this. anyway, for those that understands me, use your brain and u can work out how to apply this trick to help u to go down faster to deeper stages for the gold quest.