As far as investigator-specific weaknesses go, Vengeful Hound is relatively mild. I would say it is most like the basic weakness Stubborn Detective in that it effectively blocks out Norman's special ability.
- Stubborn Detective has +1 fight, where Vengeful Hound has +1 evade.
- Stubborn Detective's effect blanks every investigator's text box at the location, whereas Vengeful Hound's effect only works on the investigator engaged to them.
- Vengeful Hound deals one point of horror damage whereas Stubborn Detective does not.
Generally speaking, character-specific weaknesses are supposed to be worse than basic weaknesses, so if you get a character-specific weakness that's on par with a basic weakness, that's pretty good. If you compare Vengeful Hound to other character-specific enemy weaknesses like Sacrificial Beast and Graveyard Ghouls, I think it's much milder. In fact, I think even Stubborn Detective is a tougher weakness since it has a harder fight and you really don't want to be evading these types of smaller hunter enemies anyways.
I think this weakness was made weaker because Norman Withers has such low and , but he has plenty of combat options to help him deal with this weakness. Mind over Matter, "I've got a plan!", and Shrivelling can all potentially take down this monster with tests that are base +2 or base +3. That's really not bad. Of course, if it's multiplayer and Norman doesn't have any combat options in his deck for some reason, another investigator can easily dispatch this enemy for him.
I'm not sure what the non-replacement cards for Norman Withers will look like. I think that the other replacement card, Split the Angle, is situational at best. However, I think it is possible people may come back to use these replacement cards even after the main cards are released so that they can continue to use this relatively mild weakness.