Their aim should be players of the Veratti mould. IMO they are going to need a new CB, a RB and 2 new CM(Assuming Rakitic stays and Gomes decides to become half decent) and a back-up for their front 3. Signing players with the required ability to play for Barcelona in those positions is going to cost a lot. I feel they're making the same mistake we made, ignoring the glaring problems in the squad and papering over the cracks with signings like RVP or Suarez. When their front 3 is clicking everything is rosy because they are unbelievable, but in games like these when they just aren't up for it, their shortcomings as a team are brutally exposed.
Now that being said, I'm only making the assumption that they aren't stacked for cash due to their business in the transfer window the past few seasons, but if they indeed aren't and they do need to sell one of the front 3, I think it would benefit them in the long run.