Inconsistent Hexblast Damage

I'm new to aRPGs as a whole, so there very well could be some mechanic or something that I am missing, but I feel like Hexblast has very inconsistant damage.

Here is my understanding of how Hexblast works. It pops all curses in the area on enemies. If 2 enemies are within the explosion radius, the skill essentially double dips and both enemies get hit twice (1 hit per curse detonated). This scales up to 9 curses.

My issue is, I will randomly do basically zero damage with Hexblast to any enemy though. But other times I one shot the same enemy.

Here's a little example clip of what I am talking about. In the first section, I cast Hexblast and every single ad that spawned with the rare died instantly (I also think they looked too far away to even chain damage so that was only with a single curse pop per enemy). In the 2nd half, I walk into the very next room with 3 enemies right next to each other and 1 by himself, spam Hexblast about 5-6 times and not a single enemy is dead.

https://www.youtube.com/watch?v=ULHvfab1Nb4

I've run into dozens of other examples of this happening, even with the exact same enemy. My first handful of Hexblast's will just tickle the enemy, and then all of sudden they get turned to dust in the very next cast. I don't think it's random crit rolls either because neither Detonate Dead nor Bonestorm run into this type of inconsistant damage issue.

What am I not understanding about this skill? Besides Detonate Dead, it's basically the only ad clear in the Occult tree. I would also love to take off Detonate Dead because I'm trying to go for a bloody chaos build and obvious Hexblast fits that theme way more than a fiery explosion.