Yes for the basis of understanding the function. Using my example at the top, if you add Equivalence mythic then your damage reduction would become:
1-(0.35x0.75x0.6188x0.8434) = ~ 86.3% Reduced Damage
0.35 = 1-65% for equivalence mythic. Bae
0.75 = 1-25% for Defiant set.
0.6188=1-38.12% for Armor
0.8434=1-15.66% for Resist.
The example at the top had 61% reduced damage. Therefore, using Equivalence mythic in the exact scenario I provided will increase your damage reduction another 25.3%.