Delphox works pretty well with Scarf Basculegion in my opinion. They wear each other's checks down and Basculegion's pivot can bring Delphox on Pokemon such as Magnezone, Dragalge or Wo-Chien. Basculegion also scares Tyranitar and Slowbro out.
Bonnet's not really that good right now due to the abundance of U-turn and better Grass type options being available. If you want to check for teams go to the Sample Teams thread https://www.smogon.com/forums/threads/sv-sample-teams-submissions-open.3717072/
HO is very good at the moment, it would be safe to say that most people who got the reqs for Lilligant-Hisui's suspect used HO for instance. You have a few of them as sample teams if you want to try using one.
I wouldn't say it's bad but it sure is overshadowed by rain as of right now. Tyranitar and Hippowdon being in the majority of teams makes it hard as well. Moreover, unlike rain, sun lacks fast abuser, especially since Lilligant-Hisui's ban. Not bad but definitely niche.
It's used pretty often in HO as a Tera Ground sweeper. It has the obvious double weakness to rocks and doesn't always hit the hardest without Tinted Lens, but once it gets the Throat Spray +1 and a few Speed Boosts it can snowball if played right.
At the time that viability list was made, Yanmega hadn't been optimized yet. It's currently one of the best Pokemon in the tier with the following set:
In RU (their respective tiers), Slither Wing can be a defensive pivot using Heavy Duty Boots or a Scarfer with pretty great attack. Forretress is a hazard setter / spinner with a slow pivot (volt switch). Noivern is a defogger or Specs / Throat Spray Boomburst / Draco wall breaker.
They are all versatile pokemon that have multiple roles, and 2/3rds of them even do those roles well.
It's not a thing of being outclassed, more like "there's no place for Ice types in the tier outside of Snow. And even then it's a questionable choice".
It's just really restricted to certain kinds of teams, and right now hyper offense teams have so many more broken sweepers to use. Drednaw will never be used on any kind of team that wants to play more than 15 turns, and it's hard to fit on a hyper offense team that wants jugulis, yanmega, maushold, mimikyu and lucario. Plus I feel like most hyper offense players are copying teams from one or two popular rate my team posts, they're not the kind of players to experiment with oddball sweepers.
Cyclizar:
They're both good mons for bulkier teams, though Vaporeon seeing more usage is likely because of Wish pass capabilities. Neither of them have enough offensive presence to warrant a higher rating in my opinion as they're susceptible to getting used as setup fodder for the more Hyper Offense teams once they're chipped down.
Rhyperior is a funny mon to use as you can run a generic rocks bulky set that is slow but dangerous or a rock polish weakness policy set to potentially sweep your opponents, though neither are really viable unfortunately.
