I've been using extracts and instants for about 1 year and never had any Derma Ick issues. So when I decided to dive into preparing and drinking Kava with root powder, I thought I was immune. So I was happily experimenting away (drinking about 3 to 4 cups of various preps per day) and then Bam I got a bad case of Derma Ick on my nose, eyelids, hands, etc. So I had to back off (went back to extracts only for awhile) to alleviate it. I can't prove it, but I believe it was because of the way I was filtering the Kava and letting too much root solids through. And I think I was consuming too much of the solids.
So now I'm going to go to great lengths to filter as much of the root solids out as I can. I'm so paranoid right now about, I'm thinking of putting a triple bag filter inside a triple bag filter.
So based on my experience I would say no your prep is not overkill for fine grind stuff, but maybe you could lighten up the filter for coarse stuff. Someone posted to me once earlier (when I was complaining about stomach problems) that I should stop blending my Kava. At the time I didn't understand why they said that, but I do now. The blending grinds the Kava down to something even finer that from what came out of the bag. Between the blending and only filtering through a relatively coarse nylon filter was (IMO) the reason for my case of Ick.
My unpleasant experience with the Ick is the reason I'm now experimenting with prep techniques trying to get my Kava solids to sink to the bottom of a jar and let the water with Kava oils float to the top and then skim this off (like fresh moo-cow cream after milking a cow, if you've ever worked on a farm like me). I would even be willing to try a centrifuge if I could get a hold of one. I know a medical technician, maybe I can get her to sneak a batch into the lab for me.