Diamond Heist is probably the most hazardous map of Payday. In addition to the alarm boxes that are randomly dispatched in the level and the evacuation point that can be anywhere on the roof OR nearby the safe's entrace (2 floors below !), there are two other big variables (and you'll need to be lucky with it in order to get the "Shinobi" or "I pushed the button and lived" achievements):
1) Will your access codes work ?
2) Will you be able to access the secret room with the big diamond ?
Do you have any idea about the odds ?