[PC] How does Fight On work? (redux)

khashir

In the last iteration of Sharpedge's guide, he writes the following about Fight On:

"This does not actually reduce cooldowns by 10%, rather it works as follows: CD/(1+Recharge speed + Fight On). Where CD is the spell cooldown, the recharge speed is how much you have without Fight On and then Fight On is the bonus from Fight On. So say you already have 35% recharge, so that is 100/135. Now with 5 points it becomes 100/145, which is NOT a 10% decrease. So this feat is less worthless than Controlling Action, but still not good."

How does that translate into actual CD decrease? E.g., Ray of Enfeeblement has 18 second base CD (according to his guide). With 35% recharge, does that mean the new CD is 18*100/135 = 13.3 Secs?

With FO, then, is the new CD 18*100/145 = 12.4 secs (0.9 decrease)?

Also, how do I go about calculating DPS increase (as in, more generally, how does recharge speed increase DPS)?

Mod edit: removed moderation discussion.