I have two huge matched rhododendrons near the corner of my house. Suddenly, this spring, one of them had what appeared to be many dead branches on it. I was devastated. BUT I procrastinated, probably because the thought of cutting off those branches hurt so much. It would never look the same and probably was on the road to a certain doom--or so I thought.
Well, lo and behold. Today I saw new leaves on those branches that had looked so dead. I am so happy! The moral of the story: don't give up on those dead-looking branches until after the rhododendron starts its seasonal growth. :-)
(PS My neighbor prunes his rhododendrons into perfect geometrical shapes right before it's going to bloom. He has even trimmed it just as it had come into bloom....)