For me, it's always seem that the more perpendicular a light source is to the front lens element, the less flare and the more parallel the light source is, the worse. And then there is the "the flatter the glass, the more flare" too.
Seems like the "light piping" theory might apply here...can we say fiber optic properties?
For weddings (receptions) I usually put fresnels in front of my strobe heads, so if I get a strobe in the shot, it becomes a star instead of flare.
For the best flare protection, "light trap" methods are the most effective. See lens hoods for movie production and Arri cameras. The hood looks more like a barn door that is near fully closed (the outer tips of the flaps point inward instead of outward). I modified a small barndoor with a Cokin Bay60 ring and a ton of hot-melt glue to make mine. Never get much flare at all.