I think just about everyone is going about these calculations the wrong way, and it would be better to consider as a statistically
Binomial distribution with successes being X="double attack proc" with and p="%DA" is the probability that any given swing will double attack,
Each Swing is
independent and not affected in probability by the one preceding it.
Therefore the expected value of Successes (DA procs) per "n" swings with a "p' DA rate
E[X]=n*p
Thus if n=100 swings and DA%=5%
E[X]=100*.05=5
if n=100 DA%=10%
E[X]=100*.10=10
DA%=15%
E[X]=100*.15=15
Therefore the new attack rounds in the time that originally contains the 100 swings now contain n+E[X] number chances of possibility to hit, thus 105, 110 and 115 respectfully.
I sorry guys, though it is for the wrong reasons, the math illiterate people are right. You forgot the meaning of
statistical independence.
Edit: However it should be noted while each swing is independent on one and other ACC, DA, Haste, and DMG per hit are not independent from each other, and would have to be factored into "p" in order to determine damage increase. Also for the purposes of this proof Zanshin and that new WHM ACC thing are ignored.
Edit 2: realized i skipped a step