#1 - Jan. 4, 2017, 10:56 a.m.
The special Diablo II style Cow Level, CowKing encounter/achievement, at least for Sargeras, is shared with not one, but at least 5 Horde dominated realms... Illidan, Mal'Ganis, Arthas, etc..
So as soon as you kill the treasure goblin and take his portal to the event, even if you took it from a PvE instance (dungeon).. you are instantly flagged for pvp and spawned into the middle of a Horde dominated PvP event instance and instantly killed by the mass of horde, many of who are just intentionally camping the spawn point to kill Alliance the instant they spawn in...
As a corpse, I observed many horde just completely ignoring the CowKing and instead just taking advantage of the severe imbalance and instantly attacking any Alliance that spawn in..
The worse part is when you die during the CowKing event, you get no credit, no achievement, and no loot, worse of all, when you respawn, you are booted out of the event phase and are in a normal Duskwood Instance. So otherwords, you forced to get lucky and find another treasure goblin or do another dungeon, only to probably get instantly killed yet again...
Thanks Blizzard for your usual piss poor experience planning..
Proof: http://i.imgur.com/h1KukOq.jpg
--Update--
This reply points out how poorly implemented this event is: https://us.battle.net/forums/en/wow/topic/20752468601?page=3#post-53
It's exactly what happened in my instance (inside 5+ horde dominated realms, but outside none in sight).
--edit--
For those using the usual excuse PvP happened on a PvP server to dismiss or excuse something which they even know "there is a difference between PvP, and being ridiculously outnumbered and farmed.", It's been reported that this also has occurred to players from PvE realms, where for whatever reason, they end up getting flagged for PvP and/or get sent to a PvP realm's event phase.