Ah, see, I didn't see it as pure procreation. It could have been, but there was also the family aspect of the "queen"--I don't remember her name--having a son, and caring for him the way a mother, in our heterosexually defaulted society, would care for him. She was even looking for a father figure for him, in hitting on the Doctor and trying to convince him to join her in her world domination plans. It comes back to a nuclear family picture--a mother seeking opposite-gender mates for her sons, and for herself.

I can see how the Doctor could be argued to be asexual in this season. However, for me, it never went beyond a subtextual level. As far as I remember, he never outright said that he's not interested in sexual relations--and with definitely-not-asexual Ten as his predecessor, this hypothetical, and, if it exists, quite significant character change would have had to be made more clear, at least for me, to be unambiguous. Also, there's the whole River-is-the-Doctor's-wife plot that undermines the Doctor as an asexual character--not because asexual people can't have partners, but because River is definitely not asexual. (I'm remembering the exchange in Time of the Angels of the Doctor saying "River, I could kiss you" and her answering "maybe when you're older".)

I'm trying to remember the instances in Vampires of Venice and The Lodger you're mentioning, but I'm drawing a blank. I'll have to rewatch.