I think it may be wise to use the Pokemon Showdown! calculator for trying to compare base Speeds:
http://pokemonshowdown.com/damagecalc/
As I mentioned, Timid Arceus with 112 Speed EVs lets it outspeed threats up to Jolly Garchomp while using less Speed EVs and letting Arceus focus a bit more on its bulk. Your spread outspeeds up to Rayquaza while using more Speed EVs.