Whilst this tour has been massively disappointing from an English perspective I don't think getting rid of Cook is the answer. How many people wanted Cook out after the home ashes series? How many wanted him out after either of the series against New Zealand? Who wanted to get rid of him after beating India in India?
People can continue to call Cook negative or passive or whatever other insults they want to throw at him but the fact is that England's highest first innings score on this tour is 255. Is it Cook's fault that the batsman haven't stepped up as you would expect on this tour? I would say that at present Cook is still the best person to lead England in test cricket and test captaincy isn't all about putting fielders in unorthodox positions.