Unfortunately, the mob's legs are part of him, and therefore can not be individually targeted and avoided. There is scripting to avoid the spells cast by this mob, however due to the large aoe radius of them, and the non-proportionate hitbox size, running away doesn't always work by the avoidance code because it picks a random direction for which to run, and doesn't always clear the minimum safe distance.
These mobs are not specifically targeted for grinding. Specifically for this reason. I can blacklist them, but this could result in fighting tigers while kiting a giant rock monster around for a while (as it will not run from it avoiding all combat, just the combat I tell it to). That area is also not part of the grind zone specifically for this reason. I do have it go there only once to clear the one-time chests there, but if you like i can remove chest support for that whole area.
Thanks for your response, mate. It's a nasty area indeed and those dwellers are a pain in the behind for botters.
Anyway, I do see the problem now and perhaps the community has some interesting ideas about it?