I think Barcelona planned this very well. Barcelona understood that it is not going to be a realistic idea to go for the other cups or trophies. Actually, unless it is the Champions League trophy, it is not going to matter that much anyway.
So they made the right decision to go for the La Liga title. It's not like they couldn't care less about any other trophies. But the main priority was the la Liga title. And we can see what a beautiful job they have done. They are also playing well in the Copa del Rey. Let's see if they can actually go ahead in the competition. They do have the setup for it.
I don't think the loss to United was "planned" or an acceptable result for the club - it's pretty shameful to be kicked out of the Champions League group only to be kicked out in the Europa League for the right to play there. Xavi has been talking about the Europa League for the second year in a row ("it would be nice to win it"), but again he fails. They have the La Liga title this year and for that reason alone, the season cannot be considered a complete failure, but I'm not sure if it will be enough for Xavi to hold in his place in the summer.