As for the world class comment. World class is a vague term. To me all our strikers are world class. Dzeko is the most accomplished of them. 2nd best striker in Euro qualifications, top striker in current WC qualifications, 2 times bundesliga player of the year voted by the players, Ballon d'Or shortlister. Won Bundesliga first time ever with a mid table team, all time Bundesliga record holder for the most scoring partnership, won PL first time in 44 years (he played major parts in both accomplishments), Man City record holder for most goals scored against another PL side.. doesn't get much more world class than that.
The fact that he's thrived and managed to be the top league scorer despite getting the Sinclair treatment from Mancini alone tells me he's world class. What I mean by that, is that Mancini bought a wrong player. He never intended to use Dzeko for his strengths, which made Dzeko less effective, but that's not Dzeko's fault now is it?