I very much agree with everything said, but there is one slight statement I cannot simply neglect. In terms of raw talent, Rafinha has plenty of it and the fact that he has not excelled, and / or his development has stalled, has a lot to do with how Eusebio has built the current Barça B and how that in turn affects players such as Rafinha and Sergi Roberto.
When you look at the two, when they were playing in Juvenil A / Barça B under Oscar Garcia and Lucho, the two of them shone and led the way by example. During the 2009-2010 season Rafa was one of the most consistent performers for Juvenil A, and he maintained that all the way up until he came to Eusubio's team that has no balance and no clear structure. Naturally, you cannot simply blame Eusebio for Rafa's inability to adapt, but I'd wager he still has fair bit of effect on that.
Same with Sergi Roberto. Both him and Thiago were the lynchpins of Lucho's Barça B midfield that secured their 3rd place in their first season in Liga Adelante. No doubt having players like Romeu, Soriano, Nolito, Benja, Carmona etc. helped, but it only goes to show that Lucho's team had more balance than Eusebio's team have ever had. Having a mix of older players and a few exceptionally talented youngsters helped him a lot.
Just wish Lucho would've stayed with Barça B, instead of going to Roma. There could've been a high likelihood of us singing a different tune now.