It's pretty funny to read all of these posts from the outside and see the hypocrisy from both sides. This thread is littered with people admitting to sniping previous expansion content, bitching about/bragging about DPS snipes, etc.
What I don't get is you have two full guilds working together that collectively could not accomplish the following:
1. Identify that the 3rd party was setting up on the AoE spawn to DPS race.
2. Identify that they were in zone (I'll take "What is /who for $1000 Alex")
3. Identify that the 3rd party was going to attempt to interfere having previously stated they weren't interested in any "coalition" (if I am reading the history correctly).
4. Win a DPS race of two guilds vs. one.
If you enjoy the competition and challenge of open-world encounters, you get to accept the extra risk that comes with having to identify and prepare for all of the above. Since you didn't, you now get to reap the rewards of having to complete the encounter again. Sucks to be on the losing end, but you should at least be honest with yourselves for failing to execute on what I listed above. I'd be more disappointed in DBG if they actually take action against them, given the amount of flagrant bragging with regards to sniping event/epic triggered spawns in this and the official thread.
It's the Wild West bitches, suck it up and be better next time instead of whining about how shit in a 20 year old game "isn't fair for me this time".