That is the question, right? It seems like a simple yes or no question. Does your site need a redesign? Feels like a pretty arbitrary answer. Actually, it's not simple or arbitrary. Redesign isn't even your only option, nor is it always the best one. So then what are your options, and how can you tell which direction is the right one for you and your company?
Your first task is to understand the options and which situation each option is best in. Typically, you have 3 options: Total Redesign, something called a Realignment, or to do Nothing.