Supporting this. I haven't used SpDef, but Scarf can check MegaRay, Xerneas, CM Fairyceus, Mega Diancie and even Mewtwo to an extent and it can revenge kill Darkrai and Mega Gengar in a pinch with Iron Head flinches. Healing Wish is immensely useful and Trick and Body Slam come handy to cripple stuff. It's more on par with stuff in C+/C than with C-.
Also, why are Arceus Ice/Fire/Fighting/Grass/Electric/Flying/Bug/Psychic ranked at all? Do these have a specific niche that I'm not aware of, or just because they are Arceus formes? I haven't seen any of these except, like, a few low ladder teams with 6 Arceuses.
We have unranked bugceus and psychceus, so it's not an issue with unranking formes. It's just that D rank still seemed like an ok place for the ones you mentioned. Ice, Fighting, and Grass I don't see getting unranked because of lack of any real competition and they have a few small things going for them (great offensive typing, ekiller check, grass knot is like the best coverage move + better vs ogre), Electric was far from the worst thing I've used as a CM arc form with boltbeam coverage so it fares way better vs hooh and megaray. Flying is, uh, just terrible really and Fire was up for unranking but we agreed on the niche xern check being enough to let it stay or something. I have no problem with unranking the last two though.
Having tried Rachi a decent amount I could support C, bulky has a bit of a niche in the slow u-turn but definitely isn't the selling point while scarf's healing wish and normal resist are kind of cool but it falls down in not actually being able to do significant damage to anything at all. It's just so weak that you're going to need a hell of a lot of flinches or sacrifice most of your health before you can get through something like Ho-Oh or Ekiller. If this had 130 attack it'd probably be solid but it's just such a letdown. On the other hand it's way better than Aegislash, which is honestly closer to dropping than rising. No issues with Deo-S or Arc Dark either but I do have noms of my own.
The lower ranks are still really more of a "seems good" area than having a ton of thought put into them, so there are a few things which can switch around imo. Greninja could frankly be unranked, I don't want to use it as a sui lead when Scolipede lacks taunt but brings so much more to the table and even cloyster can be annoying. Plus, once it's down there's generally plenty of opportunities to defog and I don't think suicide Tspikes are particularly good because of the ease of removal. Regular Sableye is also a terribly niche mon, its lack of useful resists more than compromises any utility from its immunities. Mega has the bulk to actually take things on, but regular sableye is a status spamming mon in a meta with a ton of better status spamming mons. I really wouldn't mind this being unranked but I don't have the best experience with it so it could end up another one of the mons that are pretty terrible and have no business being ranked like whimsicott and aron. Speaking of those mons, Deo-D and Forretress still have way too much competition as suicide leads and just, why? Frankly, I think we could unrank arc fire, whimsicott (but i won't keep bringing this up because the situation of this being a terrible mon won't change and it's not at least stupid to even look at like aron), forretress, deo-d, sableye, maybe arc flying, and chansey (if we're unranking the worse stuff then blissey is always better especially with gengar rise). That still leaves most of C rank untouched but at least removing some of the stuff wasting space and making D- seem more attractive helps to thin out the VR.
Oh and I talked about scarf kyogre a while back and people were generally against it dropping too much but it's still felt so terribly niche and unwanted. Consider the fact that it's a good switch into practically nothing so you're always relegated to revenge killing and outclassed in any other regard, needs serious support just to remove the two primals unless you want to flip a coin with sheer cold for this mon to be effective, is really easy to chip away at (its few passable switchins can status it, priority, priority, priority), and is generally revenge killing in a 1v1 scenario rather than actually doing any sort of reliable cleaning on its own. I wouldn't mind seeing it switching places with Ferrothorn, which it seems like people are starting to give more recognition to like skarmory? It can be a real pain and most things that come in to kill it like Pdon don't have reliable recovery and won't enjoy a simple leech seed, and it can keep spiking on utility arceus formes which make it better in that regard than skarm. The fact is that we have a shit ton of steel types in the high ranks, and right now i think they go klefki > steelceus (puke) > skarmory > ferrothorn > dialga > mega scizor > genesect. There are somehow 4 steels in B-, but ferro is the best of them and its rank should reflect that better (which isn't a perfect argument for it to rise, but more a comparison).
tldr because my posts always end up being too long
Support: Rachi to C, Deo-S to B-, Arc Dark to whatever
Do not support: Aegislash
we could Unrank: Fireceus, Chansey, Deo-D, Forry, Sableye, Whimsicott, maybe Flyceus
Ferrothorn B- --> B, Kyogre B --> B-
