For the most part it seems like when a Lurker attacks then they get to go first. Usually the take about half of a characters health. The easier way I found to deal with this is as follows:

-Have a character in your party that has the escape ability.
-Get into a battle with a Lurker.
-Use the other three characters to attack.
-Use escape. (On the first turn so the Lurker doesn't attack again)
-Use healing items to get the injured character back to full health.
-Repeat.

Since the Lurker keeps any damage you give it then the next time you fight it, it will still be missing a bit of health. This is a slow going process since you chip away at it's health pretty slowly, but as long as the Lurker doesn't kill you in one shot then this should work. Slowly getting revenge on the super powered Lurkers, one turn at a time.

Successfully complete the game to unlock new game+. It lets you play the game again with all the Items (including Abilities, Equipment, Managraphics, Meteorites, Recipes), Money and Universe Rank from your previous games. Unfortunately, all the unlocked characters and the level of all characters will be gone.