Unfortunately it happens a fair bit. The work around seems to be to hit the chest first, and hope you don't get slaughtered while opening it.
Yes, this would be my best advise as well. To take it further, manually send your companion in first, to distract the npcs, then you grab the chest. Helps if your companion is a tank, but it pretty much works with any of them. This is also a must for objectives as well. Destroy/slice/interact with X number of "whatevers".
Being new to the mmo scene, I too had to learn this the hard way.
Oh, and if you're ever fighting an elite and have total control of the fight (IE feels like an 'easy' fight) don't ever accept a group invite while you're in the middle of it. 9 times out of 10 they want you to do the heavy lifting and they will just 'need' on the drop then leave the group, and you, high and dry.