Re: What if Tasha had survived?
Indeed, I think the OP has effectively summed up what would have been different. They could have (and probably would have) still pursued all the same angles with Worf, while keeping Yar.
It seems like it would have rendered Wesley even more unnecessary, and made an eventual move to DS9 for Worf even more interesting, as he most likely would have been less fully utilized beforehand.
"If you can't take a little bloody nose, maybe you ought to go back home and crawl under your bed. It's not safe out here. It's wondrous, with treasures to satiate desires both subtle and gross; but it's not for the timid." - Q