The man was required to marry whomever he raped/seduced because no other man would have wanted her. That requirement was compassionate as well as practical.
You've got to be sh*tting me.
If OT God wanted to do something about it, he could have told them something like this;
"If you rape someone, I will kill you. I will cut off your balls, and I will effing kill you. Not only that, but I will miraculously restore the young girl's hymen, which you morons are ridiculously concerned with, and the rest of you will damn well treat her like a virgin, or I will kill you, too."
In this isntance, God didn't even need to install a punishment. What he needed to do, since he was actually reportedly having direct contact with Israel - was to ADJUST THEIR THINKING ON THE MATTER. The issue is not even really rape - it's that your OT God did not see fit to see that his chosen people were treating each other with respect and dignity - instead he was making provisions for what they should do when they did NOT treat each other with respect and dignity. In so doing, OT God offers tacit approval of things like slavery and rape and women as property.
A REAL God would have adjusted his people's thinking on the matter. He needed to "teach them how to fish" - as it were.
And you cannot respond to this with the old chestnut that God was not going to interfere with the culture - you've already acknowledged that he did interfere when he made this nonsense law. The question is why he did not correct the ROOT of the problem, opting instead to treat the symptom as an impotent deity.