iam not sure if you have experienced the seasonal designe 8 years ago, but as far as i know in each season a diffrent class set gives a massive boost, like "10000000% enhanced dmg on skill xy" and "skill xy gets the effect of all runes"
basicly thats how you chose your gear and skills that you use. additionaly each item exists in superior versions that are more rare, but iam not familiar with that stuff. i think some even "spawn" with perfect roles. d3 is pretty brain off/ straight forward as far as i know.
check trang oule set for wd and google a "build" for it if you want some more details. but i guess the details only decide if you can handel greater rifts 150 or greater rifts 155