Callista is different, because she possessed a ship then someone willingly let her possess them and eventually in the fate of the jedi series she was valuable to the plot.coughAblelothcough;)
http://starwars.wikia.com/wiki/Mandalore Here is a list of mandalores. You will find jango and boba on that list. The clone wars confuses everything about mandalorians.
At least this isn't perfect world where the gear gap is HUGE and the distance between a fresh 100 and a fully refined 100 is giant and 2.5 stuns mean DEATH.