I wouldn't say that wolves are having a hige impact on the deer herd as a whole in Wisconsin.
That's because they are mostly in just the northern part of the state. Up there they have had a noticeable impact on the deer herd size. In the good years (mild winters) the deer herd numbers don't jump like they did fifteen years ago. If the wolf population continues to grow unchecked it won't be long before the impact becomes a major problem.