Do we need a new formation?

Would a change to 3-5-2 help us? I must admit to being concerned with our current defensive capabilities. Like most people, I love to see Andersen and Guehi passing and moving forward with the ball, but for me a fit James Tomkins would be in my defence. How about this team?

Guita

Andersen Tomkins Guehi

Ward McArthur Gallagher Milivojevic Mitchell

Edouard Zaha.