With click, it is entirely two factors.
a) the rotation used; and
b) the timing of the clicks.

I cannot answer to his rotation.
But you can tweak your own; with click this is relatively easy. Just drag your castsequence macros around, and the order changes.
You could even get extremely convoluted ordering by going:
spell 1, Null
spell 2, Null
spell 3, Null
Then sequences thereafter, so the first iteration of spells can be one order, but then due to the Null arguments they are not repeated until they reset (reset=combat), and then the normal sequences kick in, in the secondary (repeating) order.



As to (b), this will depend on a consistent click spam speed.

You should periodically check your speed, by using a clock/watch and something like Notepad. Spam away, as you do during play, to determine your clicks per second.

Also, periodically visit a target dummy and check your macro. You would want to drag each (base) spell from the spell book, and verify it recasts as soon as the dot type component has expired, but not before then. And the same for spells with recast delays; you'll want them to recast within a GCD of coming off of cooldown -- the only exception being if two become available at once, then the first should cast in GCD 1, and the second in GCD 2.