Denabol,
I totally agree with you. Pax are not told enough information about ditching and in this case if there was only 1 flight attendant at the rear then he/she has done a marvellous job in redirecting all the pax to the overwings and the forward doors. Placards would be a good idea on the internal rear doors of aircraft that shouldn't be opened in a ditching, but this can be confusing as this can be different even on the same aircraft type ( i.e - 737-300/400 rear doors ARE opened in ditching, 737-800 they are NOT opened ).
Having worked on aircraft where you are the only attendant at the rear I can tell you the thought of hysterical and paniced passengers coming towards you is a scary one - especially when you are alone. This is another reason why I hate the 1/50 ratio of crew/pax in some countries.
Ultimately the overwing briefing and safety demonstration is our best chance of pointing out these 'ditching' differences on each flight, and this accident I hope, will give more airlines motivation to update safety cards, overwing briefs and safety demonstration videos.