yes if you get it wrong you get a lower overall multiplier but theres no need to save them all and do at once
Ninja 3, Cloak, Sandman 3 = 6.3x
Ninja 3, Sandman 3, Cloak = 6.3x
Cloak, Sandman 3, Ninja 3 = 6.3x
Sandman 3, Cloak, Ninja 3 = 6.3x
other combinations net you a lower multiplier
i go the ninja 3 sandman 3 cloak and dagger route
i level up ninja and sandman whenever i want and can just making sure when im ready for level 3 i pick ninja BEFORE sandman and its golden, i always get deacons perk last
there really is no need to wait to do all at once and miss out on all that bonus sneak attack