Should Razor Shield's Mastery stack with pets?

[soon]

Arcanite Precious egg gives 25% damage reduction (stacking). Razor Shield Mastery gives 10% damage reduction. Shouldn't the two stack up?



Watch the video. I take the same damage with or without the skill. 15.947. I'm not using any pets or elixirs to reduce damage. Razor Shield's Mastery doesn't work.