A culture that include the concept of a "raiser" - an octopus with the job of raising the babies, and passing the culture on to them, without mating at all - can avoid that issue. The "raiser" would also improve his average genetic fitness if he is a sibling of one of the parents, since the children would then all have approximately one-quarter of his genes.

This is a lot less motivation than for parents.

If it's not enough to kill off the species, evolution generally won't drop the feature.

Well, for starter if you don't die after mating you might be able to mate again.

According to my source, which is a blog comment that doesn't site its sources, the death is a form of controlled cell-death and scientists have been able to remove the gene responsible and the resulting octopuses (or squid) can mate again later.