I think that "we've" let the floodgates open on having Arceus in the uber metagame via SRing and Tickets already. He's such a key part of the metagame now, with him being one of the better Deoxys counters, one of the reasons people use Giratina over Lugia, etc. If you took him out, the metagame would shift around and be confusing again.
So? It never should have been allowed in the first place. And, as I said, ubers isn't made to be a balanced tier, but rather, a tier to ban unbalanced Pokemon to so OU can be balanced. Talking about allowing certain things to balance ubers is entirely nonsensical. If it were balanced, it would be OU.
Personally since people still put in the hard work of SRing, I woludn't mind facing one.
Why didn't they just hack the Arceus directly? Both Pokemon are obtained with an AR, so it seems like self-deception to say "Oh, this is legit because it would really suck for me if it weren't.".