Barca needs to buy a quality striker this summer. Messi can't be the only player that scores in the team. I can't believe how they bought Alexis instead of Aguero (City bought Aguero pretty much for the same amount). They need to get Neymar (or Suarez maybe). And Pique and Puyol really declined. They also need one or two good central defenders. The midfield is fine. Iniesta and Busquets always play great.
Yes Aguero would have been great signing for Barça and fit in well there. Messi is a monster but Guardiola's decision to revolve the team's attack completely around him has hurt the team and made them more predictable to defend against.
In 2008/2009 when they won the treble, Messi scored 38 goals mostly playing as a winger, Eto'o scored 36 and Henry 26. In 2010/2011 when they won the La Liga-Champions League double, Messi scored 53 goals, Villa 23 and Pedro 22.
Last year no other Barcelona player reached 20 goals, while RM had 32 goals from Benzema and 26 from Higuain, alongside Ronaldo's amazing 60 goals. This year I'm not sure if anyone else has even reached double figures yet. That is a worrying trend for them.