Whether it's A+ or A, I think the three Arceus forms should be equally ranked, perhaps with Arceus-Water being ranked higher than the other three. In my opinion, Arceus-Water is the best support Defog Arceus due to its defensively awesome typing which grants it a resistance to Sacred Fire and Lava Plume, albeit it does come with the trade-off of getting hit super effectively by Dialga's Thunder. On the other hand, Arceus-Water cannot opt for any other set, but the Defog set alone fits easily on stall and balance teams.
Arceus-Ghost has been notorious since BW2 for its SD Shadow Force set that surpasses even Ekiller in raw power, while it can opt for a defensive support set with Defog, too, albeit I personally dislike this variant as Ghost fails in providing defensive utility and synergy. Arceus-Ghost can opt for a defensive set with Will-O-Wisp, too, but this is mediocre as well due to Refresh Mega Salamence increasing in popularity, as well as the rare yet always possible Refresh Ekiller (relying on Will-O-Wisp forces you to be careful in statusing the opponent's Ekiller with another status as well, giving you less freedom when using status moves as a paralyzed or toxiced Ekiller is immune to Will-O-Wisp). In addition, changes between BW2 to ORAS with Primal Groudon receiving an immunity to Will-O-Wisp, the metagame becoming less passive with things like Ferrothorn dying out, et cetera mars its previous spot as the best Arceus form.
Finally, we have Arecus-Ground. I think that Arceus-Ground was originally put above the aforementioned two due to its ability to run both an SD and Defog support set reasonably well, whilst doing the latter job even better than Arceus-Ghost. Yet, empirically, the anomaly caused by the near-obligatory use of Primal Groudon has led players to be forced to make up for the weaknesses exposed by running double Ground types on one's team via the other four teammates. Dice touched upon this and I couldn't agree more; defensive Arceus-Ground is very hard to fit on a solid team when one chooses to run Primal Groudon alongside it and, in addition, I personally find Defog Arceus-Ground to be extremely difficult to play with well, as it relies on predicting correctly when to use Judgment against the opposing Primal Groudon as opposed to Toxicing it and pressuring with Defogs to clear Stealth Rocks. So much so that, honestly speaking, the only player that I have seen use Arceus-Ground well in any context so far has been Level 56 alone.
In short, Arceus-Water, -Ghost, and -Ground should share the same spot in ranking because Arceus-Water is the most consistent and most easy-to-fit Defogger but loses to Thunder SR Dialga, Arceus-Ghost's SD set is a slower and deadlier Ekiller but its defensive set is the worst of the three, and Arceus-Ground, while its SD set is arguably equally as threatening as Arceus-Ghosts, and its Defog set almost as good as and sometimes surpassing Arceus-Water's ability to fill out this role due to it not losing to SR Dialga, is generally less consistent in keeping hazards off the field as it is less passive and is more difficult to fit on teams due to the omnipresence of Primal Groudon, causing an overlap in typing variation.
