I tend to agree with the notion that suffering has a purpose. But in a different way, I guess, basically after many years thinking about it and suffering depression.
The influence of Krishnamurti's teachings also made me understand that suffering is not necessary, and it isn't needed to grow or learn. Rather, suffering is a consequence of our misunderstanding of reality and ourselves, an effect to a cause, if you will.
Don't take me wrong, what suffering does is put you in a position where you have no option but to look inside.