Hounds de facto force everyone to play reaper since they function as both a Fear and Carnage reaper. If a person comes into a quest late and a Hound spawns on them it can and has wiped entire parties by putting the Dot damage on everyone. Hardcore doesn't mean, to me anyway, Diablo Hell mode. I enjoy HC for the full groups and team play. These hounds have cast a long enough shadow over season 6 that they have about ruined my fun. If I wanted to run reaper on Hardcore I'd run reaper. I don't want to run regular questing and face a combo reaper disguised as a dog for three months. This mechanic borders on an epic fail.
I do concur, I guess, with some of the points that it is better to find out about the Hounds with no time investment instead of them appearing in Feywild (although I still feel Korthos is too much and offputting to many players) when you have a day into the character. The Dot is a real issue. Anytime 90% of the deaths are coming from one source, then that source is overperforming.