100% agree. I'd have to rely on leaving a stud out of the shootout and then bringing him/her in (assuming I'd even spotted Nightmare at Noon coming), making the Grey Man in to a stud or using one of my only two (!) copies of LeMat Revolver to get myself out of range.
Fair to say that this would be likely to wreck me unless the above unfolded or I gut lucky and hit Nightmare at Noon with a Sight Beyond Sight...
I think most horse decks would struggle against it as most easily accessible studs via starting posses/the Regulator outfit ability are two bullets. On top of that it is hard to fit in weapons to boost bullet ratings as your horses are eating up your Heart slots (my 3/6/7 deck at least had shotguns to add to the LeMats, but my 6/7/K version doesn't!).
As in many ways (e.g. against Control) your Robo-regulator version is far more resilient than my deck due to Yagn's Mechanical Skeleton. I like that there's a variety of approaches that can be taken here.
Unsurprisingly, people on flesh and blood horses are less resilient than people encased in giant clanking robot suits when the town is turned in to a nightmare of blood sucking tumbleweeds.