I personally agree with most of these, Refresh is more or less useless since status is rarely used as a means to check ekiller (except on stall, which is becoming increasingly unpopular), and it gives up valuable coverage, forcing one to run ESpeed and Shadow Claw to actually touch bulky ghosts meaning Primal Groudon suddenly becomes a huge problem as it doesn't need status to beat that Ekiller variant 1v1. CM Grassceus is also useless in most situations, it performs well against other support Arceus but does nothing but kill momentum otherwise. 1 turn to set up, giving a free switch to the opponent's counter of choice, and you still can't damage Ho-Oh, Lugia, Klefki, or even Lati, it's just too limited by 4mss. 4 attacks is as well, but much more viable imo since it can put immediate pressure on some of the aforementioned. As for Arceus-Water, the 168 EVs in Speed should only be used if carrying Ice Beam. Arceus-Dragon seems to me it could be viable against some teams, if only because it can set up CMs on stuff it forces out and bop the switchin with a coverage move, though rather situationally.
Yes to removing scarf Dialga, it's just a terrible set, doesn't have particularly great coverage and doesn't have the power to make up for it either. Move 4 should be Toxic / Fire Blast imo, if only because Thunder never hits and Toxic cripples Arceus-Water and Lugia more in the long run. I think toxic should be slashed with twave, Toxic hits Groundceus and is more crippling to support mons but most of Gira-O's common switchins (Xerneas, ygod) dislike paralysis more. Also agree with using a faster EV spread for Yveltal to outspeed most support Arceus and be able to beat them one-on-one.