Sab,
A pefect, loving designer would not:
1. Create something without foresight of the suffering his creation could cause.
2. Create something that had to cause suffering out of necessity for its own survival.
These flies serve no purpose but to their own ends. Even reciprocal altruism arises in nature from a selfish desire of a species to protect its own life, or its genetic descendants.
Why should purpose involve suffering? Is there a law somewhere about that? Show it to me. Your position that suffering is required because we suffer is rather unfounded. If you were coming from an evolutionary standpoint, I could understand. However, this all seems a bit too clumsy for a grand designer.