Last season was a problem of management more than anything. Messi was injured at the start of the year and we had to integrate Neymar in his first season (which went quite well all things considered). Even so we only had 6 league games where we didn't score which, although is a lot for Barca in recent years, is not time to press the panic button. Why do you think that having another forward will guarantee more goals? Haven't you seen that we have tried that with Ibra, Villa and Sanchez? Neither of them scored a hell of a lot of goals. We have goals and the invention in Neymar and Messi. Pedro isn't goal shy either and Iniesta will always give us that creative spark in the middle of the park. What we need most of all is a coach who understands the Barca way of playing and is respected by the players. We need someone who can get the best out of the current crop of players to succeed. Buying another striker will not guarantee goals.
However, getting a CB when we don't have any will guarantee us a stronger defence.