I don't think Barca is a good fit for Mandzukic, he is very strong in the air but not the best technically and I don't see Barca changing their game and starting to cross the ball from flanks. But maybe they should consider changing game plan in the games where opposition parks the bus and standard tika taka football isn't enough to break them.
I believe Mandzukic is smart enough to know his line of play does not fit in with Barca strategy or else we'll see a replication of Barcelona been a bed of career-ending as some people you to say.
The player is still young though.
Only reason why Barcelona thinking about Mandjukic now is fact that they don't have enough offensive players right now or at least ready to play.
Mandjukic can be great "backup" plan or plan B but obviously he don't have chance to play much in Barcelona now or later.
Much better option for him is Bayern or Dortmund, in my opinion
He is not young any more so he should make wise decision now, where to go.