Marksmanship on Alpha has an APM of about 40 right now when played correctly. Lot of room for improvement there, new spec.
Marksmanship on live has about 10% more depending on the fight. My rank 1 Archi is a 44 APM. Not as much room for improvement.
So even with the GCD bullshit the sky is falling over because the spec is oh so slow, it's still only ~10% "slower" than Marksmanship is on live, and keep in mind that Marksmanship on live has 4pc going for it and shit like that.