not really. at 100% alacrity, you hit twice in the same time. ergo at 100% Alacrity, your forcequake will channeling 3 secs faster, which allows you to cast two of them in 6secs. At 32% Alacrity, your forcequake is reduced to 5,04secs. This maths includes the gcd.

Hmm, the 3 second channel with 100 % alacrity is right, but I don't know how you got 5.04 s at 32 %. The formula is cast time / (1 + alacrity). With 32% alacrity that's 6 / (1 + 0.32) = 4.55 seconds. A gcd would be 1.14 seconds.