3%?

It feels more like 20% when it is active. I was ALARMED when Selene used it, how/why is it doing this?

Is this 3% boosting the character's current value and the scaling being on an exponential curve?
IE: Say I have 1000 spell speed, 3% of this ontop of current value = 1000*0.03 = 30 more but because of an exponential curve this 30 carries more weight than the prior 1000.

Selene feels incredible at present. When that buff gets going skills fly.

Exponential curve for the record: