I have three hives of bees in central Florida. One of them had a large cluster of bees on the top of the hive. There were also three or four dead bees at the hive entrance. The hive next to that one also had two dead bees at the entrance. My question is: if these hives were being robbed, would the queen and attendant bees go out on top of the hive or would they stay and fight the robbers to the death? I decided to hive the cluster and gave them a couple of frames of brood with some honey from the hive they sat upon. There was no foul smell or sign of disease.
If it's only a matter of the odd few dead bees, don't worry, it's probably just natural mortality. You only need to worry if the numbers rise to hundreds. Meanwhile, if you're worried about the possibility of robbing, have you reduced the size of your entrances? If not, it's best to do so to be on the safe side.