Under Assassination:
Fleet Footed - Increases your chance to resist movement impairing effects by 10% and increases your movement speed by 8%. This does not stack with other movement speed increasing effects.
Under Subtlety:
Camouflage - Increases your speed while stealthed by 15% and reduces the cooldown of your Stealth ability by 5 sec.
Pretty sure I already know the answer, but if I have Fleet Footed and Camouflage is either one useless while stealthed, or is Blizz kool and let them stack while stealthed?