The Blue Waters is pretty much the far North of the beachfront hotels, and all the buildings on the right, for quite a long way down are blocks of flats/apartments, so in terms of hotels, its fairly isolated from the rest – the closest is the Suncoast cAsino, which is itself, fairly isolated from the rest of the surrounding hotels.
Its quite possible that you are not aware, that behind the beachfront hotels, to the South is Point Road – notorious for prostitution and drugs, and all the various crimes that go hand in hand. My bet is that the murders you mention took place in that area, and while geographically close to the hotels, a million miles away in terms of everything else.
Hotels routinely warn guests not to wander at night, because in general holidaymakers have no idea which areas are safe to walk in, and which areas aren’t (perfectly understandable), and can easily stray into no-go places. From your hotel you would have been perfectly safe walking to Joe Kool’s (along the road in front of the hotel, not the beach road), provided you didn’t decide to take a stroll the the Sunken Gardens (not a place to be after dark – muggers hang out there in the evening hours) The stretch of beach promenade in front of Joe Kool’s is safe, and standing on the end of the piers watching the waves at night is cool – and if you’re here in July, watching the night surfing is great from the ends of the piers too :)
Personally, instead of staying in any of the Durban beachfront hotels, I think you’re better off staying in Umhlanga Rocks, 15 minutes north of Durban. You can easily reach any of the Durban attractions, and its far less citified.
There is a huge amount of violent crime everywhere in South Africa, and if you look at crime statistics for the country, you’ll find that Durban has one of the lowest crime rates in the country – lower than both Cape Town and Jo’burg. Anywhere in SA, you have to live at a higher level of awareness than elsewhere in the world, and most importantly, know where you are going, and know where you definitely shouldn’t go!