I think Bitcoins transparency with regards to transaction that's occur on the blockchain is one of the key reasons banks wont incorporate bitcoin in to their systems. Banks and clients both rely on privacy of data over transactions made to keep certain types of information secret. That information is only shared with the people concerned. For example Apple wouldn't want a transaction sent to a parts supplier to be disclosed as it might cause a leak in sensitive data revealing their future plans. This in my opinion is the one reason banks would never employ a public chain for transacting. They are however using blockchain technology to create private chains that would give it the features of the blockchain that are so revolutionary whilst tweaking it to solve some of the problems you mentioned in the article. 
The one thing i can say about the security aspect of Bitcoin is that whilst it maybe be insecure for individuals, atleast if there was a hack only the hacked accounts would be compromised as compared to an entire system being hacked and a lot of data being stolen. Its harder to hack 10,000 computers individually than it is to hack 1 central system. Thus a Mr. Robot type financial meltdown would be less likely to a financial system when dealing with Bitcoin.