Your arborvitae are suffering from a very dry and windy winter.  Our snows this winter were dry vs. wet and as a result many of our conifers have suffered from lack of water.  Without water available for the roots to bring up to the needles, drying and browning occurs.  I had to cut down 9 alberta spruce because they were all more than 40% brown.  Wait and see where new growth emerges before giving up on your arborvitae.  Also, the cold blustery windy days "burned" the needles.  Depending upon how much damage the trees have, they may recover.  Make sure they are getting sufficient water.  If your bushes are not too brown, they can handle early pruning, and respond well even to shearing. It is best, though,  to wait before pruning. Your arborvitae may be brown, but not dead. If too much is pruned out recovery may be severely delayed or not occur at all.  Early spring pruning works well with these species because the new growth covers the pruning cuts. These can also be sheared in late spring or early summer, but once the new growth is in make pruning cuts carefully so they are covered by existing branches. 

Thank you!!

We had a very hard and harsh winter this year.  We had many days of very windy, cold windy, days and the snow we got was mostly dry (rather than wet and heavy) snow.  Most winters in WI have many wet snow days.  The wet snow waters the trees over winter keeping them from dying.  I think you could say that this winter was a unusual.