How exactly Wither works?

Hey mates

Tooltip says debuff lasts 0.5s - does it mean this is how long a single stack last,or channeling not only adds another stack up to 20 total,but also refreshed duration of the debuff?

0.5s is the hinder duration, which is pretty useless, 2 seconds is the "secondary duration" that is per stack. That is what the wiki says, and that also makes sense from a balance and logic perspective

EDIT: So with zero cast speed or duration increases, 1/0.28 = 3.5714 casts per second, times 2 seconds, = 7.14 stacking casts, or you "cap out" at 7, which of course can be increased via cast speed and duration

The increased duration mentioned by the previous poster is even more useful when combined with a spell totem, as not only the wither effect will last longer, but the totem aswell.

I see.Kind thank for you guys for clarification.