This build has less DPS than my 6 Lightning Tower but it needs less repairs. You can lose if spiders web your units, Sharken push the wall, or Djinn eat a buff beam. The reflect beams are everywhere because of Spiders. Upgrade the buff beams before the wave.
Hint 1 Boost Monk position.
Hint 2 Ogre Copter drop locations. Lightning immune Copter Ogres can land at the north location if your Lightning Towers are on cooldown. These can't damage the Crystal, so it isn't an instant loss if it happens.