if you use driven teams,i'd say boith saga and musshuru have uses...
One thing I will add to this...low CD characters like Saga and Musshuru are nice for speedruns, which is normally more of a convenience thing, but with Neo/Kai Clashes coming to Global, speed becomes more important than before. You want to clear the raid as fast as possible in the 30 minute window, and the lower your CD, the better. And as it turns out, Slasher and Driven are two of the classes featured for QCK Mihawk...
That doesn't mean you necessarily need Saga or Musshu, but hey, farming a colo is rarely a bad idea anyway since you'll get CC and Socket Books on top of the character itself.
Also on Musshuru, if you haven't gotten around to farming him yet, it's worth noting that Invasion Shanks is pretty much perfect for his level, and with the Anni Sunny active his CD is irrelevant. I'm running Double Croc, Raid Kuma, 3D2Y Robin, Invasion Shanks, and Sengoku (who can be replaced by any solid PSY Cerebral, such as Momonga). Enter Wapol's stage with over 10k health, wait out the 3 turns of Bind (meaning you need Bind lv3 for this team), then use Kuma, Robin, and Croc to burst him. On Musshu, use Shanks and Croc and clear.