Houndour is not a good mon in a tier with many good stealth rock setters (onix, tirtouga, ferroseed, dwebble, pawniard) and its immunity to fire is fairly irrelevant. Its usefulness as a psychic answer is not useful considering abra is not as good without magic guard. It also adds to a team's fighting weakness which is rarely good since we're lacking some fighting resists (regen foongus/slowpoke mainly).
Murkrow and misdreavus are probably the 2 most banworthy mons that exist in LC currently, so I'd say discussion should be mainly on those for now. Murkrow has insane versatility and great base stats (also hitting 19 speed), which makes predicting what moves it has very difficult. It also has stab sucker punch to ruin the days of any scarfers that try to revenge it.
Misdreavus seems slightly more manageable personally. Running knock off on timburr/mienfoo will cripple misdreavus bulk a lot (and knock off is a god move in LC anyways, even with low base power). It also has the trade off of running speed or bulk. Sure it can hit 19 speed, but it'll also be a lot frailer vs scarfers/things that can tank a hit. It also doesn't have nasty plot so its offensive presence is a lot less than what it would be with nasty plot.
Another food for thought. Shell smash users. I only watched the finals match of the recent lc tournament so I don't know how much shell smash users were used, but they are quite powerful and difficult to stop. Shellder, clamperl, tirtouga, dwebble are a few that come to mind. Shellder has reasonable physical bulk, which allows it to set up on certain physical attackers, and it has flexibility in its moveset to some extent with its last slot. Clamperl has insane power behind it, but is more difficult to set up/not get revenged by sucker punch etc. Surf+hp fire coverage gives you all the coverage you need at +2 sp atk. Diglett can be used as a support for any shell smasher. It can remove pawniard, a troublesome pokemon for smashers due to its typing and stab sucker punch. It can memento on a threat to allow a shell smasher to set up. It can pick off anything low hp that is slower than it.
Diglett will be one of those annoying mons in LC that will be extra annoying without team preview. You'll have to second guess pressing volt switch with magnemite or chinchou, fearing the diglett popping out from its dirt hole. I'm not sure if diglett will outright be banworthy, since it has low power and low bulk, meaning it has very little that it can outright ko, even if it gets in safely. It's definitely something to watch out for in the future, most likely for potentially unhealthy teambuilding constraints, but I guess we'll have to see how the LC meta evolves.