Works best with two ranged DPS. Ogres will rush the forest golems instead of the crystal. Could use up the DU for reflection beams but I never needed them. Odds are if you are at this point, you have much stronger stats than what I had.  Use extra slots as you like. if your resistances are good enough to not need a healing aura, replace with empowering shrine. A buff guardian summoner is recommended.

1. Should have enough mana on the ground to max a 6 DU buff beam running through all the towers then 1 star the mortars. Use remaining mana to upgrade electric auras.

2. Station your stronger ranged DPS and split screen auto-fire at this door since the enemies are closer.

3. Use your Second DPS actively on this door to catch harbingers and ogres running off to the side. 

It CAN work on nightmare as well if you have better tower stats. But running it on insane is much more consistent if you have low stats.