can confirm this happens even in dungeon, no damage.. not falling, just died instantly.
Sometimes this is due to lag. The boss will cast an ability that is damaging to you right under your feet, but because you are lagging, it won't render on your screen and a few seconds later, when the visual of the ability may have disappeared, you will suddenly take MASSIVE damage and die instantly, and the visual may never render due to the client skipping frames to keep up.
Botters will see this as very odd and unnatural, because their bots are running either from the same machine, or from the same network and nobody will tell them "dude get out of this shit", or "why did you not move or use cooldowns". Someone botting a dungeon on 5 accounts will be absolutely oblivious to what has happened and will be like "OMG invisible GM killed me", when in fact you are falling victim to lag and the way WOW covers it up to make things look smooth on player screens.
Players can also use lag strategically to achieve the same effects. You are merely experiencing what happens when the server does it to you.
Also, the game has the habit of killing you, if it's ever in doubt that you should have died to something, but for some reason you didn't and instead barely survived with a few points of health left, which actually happens pretty often with bot CC's.
There were numerous bugs in MoP from the start, the most famous one being "the floating sea of skeletons", which was not only present in the Beta, but on Live and sometimes you could see it as you quest around. I have seen it once as I leveled my Rogue to 90, and it was quite funny that such a bug made it into the production release.
I can keep counting bugs, but you get the idea. This expansion is a massive bug fest due to the drastic overhaul of the world and all the classes, so you are probably dying to bugs, which manifest themselves in places and ways they shouldn't, like the bug which allowed you to see The Lich King walking under Stormwind due to the way the map of the world works.
Basically, the damage that killed you in Goldshire may be from an event that happened on the other end of the map and somehow the server decided you were close enough to it to be affected.
Keep moving, nothing to see here, at least not anything that should be discussed too much and too deep on THIS forum.