A double pivot of Martinez and Busquets would've been a lot more secure defensively. If it means giving up a player like Pedro or Mata, so be it. Without a double pivot, Nigeria and Italy ran through Spain's midfield at ease; let alone Brazil. Brazil could've easily scored 6-7 if their finishing was better and they had slightly better decision making.
Double pivot =/= counter-attacking football. Bayern play with a double pivot and theirs is a balanced possession game. Spain have played with a double pivot for the past 4 years and they are nowhere being a counter-attacking team.
We don't really need to play double pivot per se, but for difficult matches, we could play with 2 strong players in midfield like Pep often did in our away matches for CL knockouts. Yaya-Busquets, Yaya-Keita, Busquets-Keita