The comments on Wowhead's page on Furious Attacks says that it doesn't stack with MS (or Aimed Shot, or Would Poison):
Furious Attacks - Spell - World of Warcraft
There's a link to a forum post which presumably has a blue post in it:
World of Warcraft - English (NA) Forums ->
But the forums are down for maintenance right now so I can't quote it.
Also bear in mind that even if they did stack, it would be multiplicative, not additive so you'd get 75% reduced healing, not 100%.