I've noticed in some fights my goblin trio literally stands there and gets beat up without moving or attacking. Please see that this issue is looked into and corrected thanks.
I don't have a problem with Goblin Trio at all but it may be beneficial to you to post a video and possibly how it is runed (although runes shouldn't make a difference) to show the issue properly.
Have noticed exact same thing since red update. Just stands there. Not breaking apart.
i too don't have a problem with trio..