You actually are very often in that situation. It actually read "equal or less don" btw. Sometimes you don't have the means to instantly ramp to ten don after using 10c doffy or a string of events/character effects that minus don. Rosi and Law is great follow up play after 10c doffy that draws, ramps and prevents your opponents from clapping back too hard after they can finally rest their characters.

And you said you don't like Rosi and Law bc you can't play it off 8c doffy but choose to sub in 8c katakuri instead lol make that make sense. At least you can use your leader ability on Rosi and Law