Thanks for this thread, OP. It was fun reading about the characters' ages and backgrounds. However, I don't necessarily agree that this is a problem yet, because we are bound to get countless more heroes in the months and years following launch. Blizzard has proven that they care about diversity and equality, and I trust they'll create new female heroes that aren't all young, fit and pretty.
side note: I thought it was interesting that the antagonist in this year's DOOM was an intimidating older woman.