I don't know about trainer lock being a big problem for Arceus. I've played and beaten Vilegar variants before without much trouble. I guess it all depends on the number of Trainers in ones deck. Mine runs 6-8 Trainers total with heavy Supporter lines (Collector,Bebe,PONT,etc) to counteract it. Also, since you play no major Poke-Powers, Gengar will have a hard time damaging you for 60+ damage with Poltergeist. The only thing that really hurts is Gengar's Feinting Spell. Even though you can OHKO Gengar, if they spam heads on Feinting Spell, it could be a close one.
As chanman45 said, it may not be the best deck ever, but it's great and shouldn't be underestimate it.
Its a real dark horse this format.