User blog comment:GreenMoriyama/Nine, the Magus of Elemancy (collab w-Lesdin)/@comment-7709681-20170913024132/@comment-27802145-20170913173809

*scratches head

The additional effects don't stack, and the damage boost from W only affects the initial damage since that is what Cardinal Flare technically is.

As much as I hate number crunching, and this being the reason why I'm ditching numbers in my future concepts, I can assure you I thought these numbers through.
 * 200 = max rank cardinal flare's damage
 * 100 = max rank fiery garnet's bonus damage over  seconds
 * 1.3 * 1.8 = 2.34 = max multiplier for cardinal nova
 * (200 * 2.34) + 100  = 568  magic damage over  seconds with a minimum cooldown of  seconds when innate affects the initial cardinal nova
 * 1 - compare to syndra's which caps at 1260  magic damage instantaneously on a longer cooldown
 * 2 - compare to taliyah's which caps at 442  instantaneously upon collision on a shorter cooldown with no restrictions as with nine (needs 3 stacks, needs innate to have minimum cooldown)

Quite painfully in fact.