Questions about Soulrend

I have some questions about Soulrend:

1) Does the damage over time part of the damage stack on enemies? If I'm using GMP and two of the projectiles hit an enemy will the debuff do double damage?

2) Can the hit portion of the damage deal critical strikes? I want to use a flask that gains charges on critical strike. Is this possible with Soulrend

3) Does Soulrend deal ailments? Will it benefit from "increased damage from ailments"

4) Why is Essence Drain more popular that Soulrend?

thanks for your help

Debuffs with the same name generally do not stack unless explicitly indicated otherwise.

Two projectiles from the same cast cannot hit the same enemy either, although my understanding is that the damage over time debuff does not require actually hitting enemies to be applied. So an enemy can get debuffs from two different Soulrend projectiles, just not at the same time.

Yes, it can critically strike, but the investment required for it to do so regularly is definitely not worth the few flask charges you get from it.

It hits and can inflict ailments, but the majority of its damage stems from the DoT debuff it inflicts, so scaling ailments with Soulrend is a bad idea. The Soulrend debuff itself is not an ailment.

Essence Drain is more popular because it allows more time to move around after applying the debuff, whereas the short duration of Soulrend forces you to reapply it constantly which makes you more vulnerable during boss fights. With enough density, Essence Drain + Contagion also clears faster than Soulrend.

Thank you so much for your thorough answer. This was very helpful