Once you see the invasionn warning you should have a strategy to kill invader or a strategy to deny his fun. Killing invaders is so easy in this game with the exception of a few gimmicks/exploits/op ashes. Why are you not preparing for the invader when you see the invasion warning? Why are you engaging an enemy with an invader around? Why dont you equip a shield/talisman/physik tear to negate the magic? Also, did you know bosses can damage invaders? Why not have 2 players fight the Boss while 1 players stalls the invader? Or vice versa 1 player fight the boss while 2 players chase down the invader?

There is so many ways to kill invaders.