There is something you need to realize between mastering and not mastering skills. The ability to possibly make your skills from 2hko to a 1hko.
For example. Adrenaline gives 20% AP at level 10 but 26% at Mastered. That extra 6% can make a huge difference.
Another example is Flaming Fist. The magnification ratio goes from 460% to 530%. That makes a different as well.
[ I am not going to list out all the skills that have a better increase when Mastered ]
Mastering skills have a purpose and it's to do what I just said, which is changing a 2hko to a 1hko.
Side note: Have you personally tested out this build yourself?