I'm not referring to group selection. If you're living in a close community, then once you've had your chance to conceive, there's not a lot of benefit in fighting off other suitors,

If its valuable for the other suitors its valuable for you.

since you'll be helping raise the child anyway;

Yes, but you want to be as certain as possible about which children are yours so you can favor them. And, yes, even in a close knit community there are many ways to do that short of causing the tribe to break down.

More likely we'd see a diversity of different strategies.

Well, yes this is in fact what one observes.