Preheat the oven to 350 degrees F. Combine figs, raisins, apricot nectar, and honey in a small saucepan. Bring to a boil and cook for 5 minutes. Remove from heat and let stand for 30 minutes.
Coat a medium skillet with cooking spray; place over medium high heat until hot. Add onion and vinegar; cook until deep golden brown (20 minutes), stirring frequently. Remove from heat; stir in fig mixture and blue cheese. Set aside.
Place 1 phyllo sheet on work surface (cover remaining dough to keep from drying); lightly coat with cooking spray. Working with 1 phyllo sheet at a time, coat remaining 7 phyllo sheets with cooking spray, placing one on top of the other. Place a sheet of plastic wrap over phyllo, pressing gently to seal sheets together; discard plastic wrap.
Spoon onion mixture along one edge of phyllo, leaving a 2 inch border. Fold over the short edges of phyllo to cover 2 inches of onion mixture on each end.
Starting at long edge with 2 inch border, roll up jelly roll fashion. Place strudel, seam side down, on a jelly roll pan, coated with cooking spray. Score diagonal slits into top of strudel using a sharp knife. Lightly spray strudel with cooking spray.
Bake until golden brown (30 minutes). Sprinkle powdered sugar on top. Serve warm.