Only other thing I'd add, which I'm sure you've got planned out already, is that the colors are a little too soft right now in comparison to the others. Getting some more solid value would really make him pop out and stand well with the rest of em!
Excuse my illiterate artistic comment, but I think he needs to turn up the saturation a bit, and have the different gradients of color a bit of different hues (looks like the shadows are just the same red with more black added in). I guess Baker seems to somewhat use the rules of pixelart for the DDrop-look.
As for the eyes, the shape is right I suppose, but as Quady puts is, they look rather timid, plus red eyes and red hood make it look rather dull. How about giving blue or yellow a spin? They would constrast a lot better (also note that it's more in line with the other Delvers designs).
The uppermost part of the "facewrap" should me more silimar to the original art, because in it's current state, it looks like "taped" to the face as opposed to being wrapped around it.
As a last note, the Cultist is more of an upfront view compared to the other Delvers, which are more top down (good observable by the eyes which are close to headgear and smaller visible space of the "mouthpieces").
In case this all is old news to you, feel free to ignore thise post. ^^