Dark Pulse is a weaker STAB option to use for sweeping a weakened team, like dragon pulse on specs dragons. While weaker, it has the benefir of adding some SE coverage, so it's not a total waste.
Flash cannon should NEVER be used, and Focus Blast is pretty much just for ttar. It hits tran also, but you have surf and earth power for that.
EDIT@above: Flash cannon is not a situational move. There is not one pokemon that it is better against than another move, nor is there a certain group of important pokemon it hits where you would need two moves otherwise.
Sazandora can be things other than a scarfer, but it's not a good set-upper, which is what taunt is best on. Taunt works on bulky wallbreakers as well, like gliscor, but Sazandora isn't that bulky, and it has a lot more power so it's better off just going for 2-3hkos with raw DM power/ SE coverage, so I doubt it will even be used on wallbreaker sets.