I know, I know. It is a profoundly unusable monster (except maybe as a plot point). The reason why would be that I tried to replicate the abilities/characteristics of an actula creature of folklore which is inherently and ridiculously unbalanced (a couple unarmed miners can kill it with relative ease while underground but it becomes a weapon of mass destruction (seriously, I'm not making this up (heck, I even scaled down its destructive potential a fair bit))). (Also, rest assured: 3.5 is crazy but not this crazy.)
As for the spread, well, there are spells with areas measured in miles (Eclipse comes to mind, with its 5 miles radius), so this is more of a balance problem (those spells are, of course, epic spells) than a problem of stuff being poorly quantified.
Should I, perhaps, put a disclaimer on the thing (WARNING: this is horribly unbalanced and that on purpose! Do not try to use this unless you can make it make sense!)
Thanks! I'm happy to hear that!Edit: I really like the harvestman though. A mechanical "creep out" effect is really neat, particularly because I think the players would assume they're going to get jumped by something else while dealing with it.