Monk Epic Fist... is it REALLY that good?

[Nordenwatch]

I was soloing HS on my monk and I was thinking about the epic fist. So far I had been using fist/SoS til major shielding and then switch to fist/AC for the stunning blow proc, but I switched to ac/sos and it seems to be better DPS.

I know that the epic fist is ridiculously fast, but if you think about the amount of haste percentage that you have you benefit much more from the haste by having slower weps. So by using AC and having 40% haste from the epic and 27 from the RBG, i have 67% haste. This haste on AC (15/25) makes it 16.625 delay if I'm doing my math correctly. So the wep becomes a 15/16.625 with stunning blow. The fist is 9/16 before haste and 9/10.64 after.

So is the whole idea of using fist/SoS flawed? I know tons of monks do it... am I doing something wrong in the calculations?