Raphinha is not good on LW imo.
I would play Raphinha at RW more often than Dembele personally, and would use Balde RB and ask him to do more overlaps and occupy higher positions as to allow Raphinha more to cut inside and occupy a slightly more central area, much like Messi and Alves in 2015.
You have to provide width, but it doesn't have to be the winger that does it on almost permanent duty. Xavi needs to learn to be more fluid, because you need to put your best players in the positions they love to play in and where they can do the most damage.
So whether you use Dembele or Raphinha at RW, this should change the type of moves the corresponding fullback will be tasked with doing. Alba LB and Balde RB is a good option until we hopefully sign a top quality rightback.