All names of bosses are in the order and spelling that Blizz put them in the Achievements (unless I make a transcription error). Dungeon names are in alphabetical order. Note that data may be incorrect or incomplete, as well as subject to change, due to the fact that this information is from the beta.
Note also that some achievements are only to kill a certain boss, and not to clear an entire instance, which explains why some instances only list one boss.
Clearly they haven't gotten many of the raids into the data files yet, but that's not too surprising; it makes sense for endgame content to be made at the end.