Speed vs attack/damage per second calculations?

by Vexidius posted Sep 24, 2018
At what point is speed better than attack?

My questions are mostly regarding jewels, as speed jewels give a bonus at 4 mounted, vs 2 for offense or critical.

I checked becken, going from 4 attack and 2 critical to 4 speed/2 atk, and his attack dropped from 1687 to 1624, crit chance from 39 to 34. The rest improved by one or a few points, and speed went from 8 to 9.72. total power dropped from 27.5k to 26.5k, so my question is regarding calculations in battle and how to see what the damage per second should theoretically be.

Thanks! :)