New Ezreal - Mystic Shot + Essence Flux on Epic Monsters

I noticed in the practice tool, that the essence flux will absorb damage from a mystic shot, and make the ability almost useless to trigger the W. It seems to be more beneficial to constantly use W into an Auto attack, and just use Q for resetting the CD, as it was doing 500 damage on its own to base MR stats. (Abilities would just not trigger the Essence Flux damage proc, but consume the debuff in the process) Ive tried everything for popping the W, and the most it adds is 150 damage, or it will just use whichever ability deals the most damage.

I noticed im doing full damage to champions with these, but to neutral monsters its heavily reduced. I was trying to do mental math, and against baron (120 armor, i believe 60mr) I was doing 1078 with W+Q, but only 950 with W+auto attack, but my Q damage on its own was near 500+, and auto attacks were doing 131 damage. I know the armor/mr make a big difference, but It shouldnt be 120 damage different from an auto attack, compared to a lichbane proc'd mystic shot from a full ap ezreal, right?

Is this working as intended, is my math wrong, or should the mystic shot damage still be added into the essence flux detonation?