With EV2 you can get inside, or behind spawns and build inside. Many enemies straight up ignore these defenses, which can easily be exploited.
To reproduce it, you only need to get out of the map with the EV. I can do this on liferoot, betsy's map, temple of the necrotic, forest crossroads... Here's a video of an example: https://youtu.be/2f3hb5BZfA8
I used to be able to do it in dragonfall gates, but I think you guys fixed it?
On temple of the necrotic, directly to the left of where malthius is, the invisible wall is "angled". You can fly against it, and will slide upwards at high speed: http://imgur.com/a/FPftM
Can't do the betsy one, since I don't have the glaive of storms to float, but you have to move away from betsy and from there, get behind the spawn (careful with the invisible kill wall).
Can't test much, because it takes me a LONG time to join and leave a map.
Here's a thread of a guy who got out of throne room: https://dungeondefenders.com/2/topic/141480/interesting-location
Can you provide some steps on how to reproduce this, and what stages you are able to do it on?