Hi @Awkward .  Its possible that LoneWolfMcquade (Essentials author) used a very early version of Tenebris, but thats just a guess from me.

I tried checking the Tenebris link on the Essentials steamworkshop page but Actkqk has closed that page.

But the last mention of Tenebris in the change notes is dated april 2017 (update 4)

Basically, both of them use the same Tenebris, it's just that in Essential there is a slight change to match the taste of the author of Essential mod.
He also does the same thing in other classes in Essential mod.

Whereas the Tenebris Variant mod uses what is available without changing it, especially in the skill (Just adding all faces, hairstyles & hair color).
Previously, the Tenebris class on Variant mod also made changes to its skills, such as changing the starter skill & unlock level. But because of the author's request not to change, then it is changed back to the original version before it was changed (v.2.0.5).

So if it depends on which one you prefer, if you prefer the Variant mod, then put Variant mod above the Essential mod.

Note:
Tenebris in Torchlightfansite is the latest version, for a long time the author finally re-updated the Tenebris class (v.2.1).