This is an easy way to kill Nexus, but it is best with a friend or at least one random player who you can communicate with. All you need to do is get into the safe spot and dance while the other player doesn't jump down and shoots rockets from the ledge. If they run out of rockets then hopefully you have some ammo synthesis on hand. A sniper will work well too. Just make sure if the player on the ledge shooting the boss dies they back out from the strike and rejoin. They will be alive again and can go back to the ledge to shoot the boss again. Rinse wash and repeat. Just be aware that a high level Minotaur will spawn on the ledge to prevent you from succeeding, but it isn't impossible to take out. Good luck and happy coin/material farming.