It's always a good idea to remove as much of the waste with a more efficient tool no matter what the routing operation. If it's a hole or mortice then drill the waste, skil saw in this case where you have a lap, following a pattern then bandsaw or jigsaw, etc. Routers are a finishing tool. They aren't good at removing a lot of wood.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.