GM's interfering in PvP battles?

I decided to go on the manastone battle tonight and noticed Gm's were actively killing me and my guildmates. While their participation may seems small, it puts an additional burden to guilds actively trying to complete with each other. I'm curious if this will be the new norm for large scale PvP battles? I've never seen a game were invincible GM's ran around killing people. Image may be NSFW.
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