Oscar, Neymar, Firmino and Moura are best in a direct style, especially counter-attacking so I think winning the ball back would be priority if I had the chance rather than adding even better offensive qualities which you do by changing Fernandinho out for Oscar. Don't think it would be bad to have Oscar there instead, it is fair to have that opinion but I think it may be a tad bit strong to state "you don't need all those 3 mf's" as I think it is fair to want three great hard working midfielders in terms of positioning and being tacklers and great at interceptions.
So I think it is a fine line there, do you want Oscar who will make the defense less capable of winning the ball back but spices up the offense or do you want Paulinho who makes the team world class at winning the ball back in those areas but slightly worse offensively. I would trust Neymar-Firmino-Moura to create something every match but I think Luiz, Marcelo and Alves/Maicon at the back really needs all the help they can get.