Meloetta is a must have in Psychic monotypes, since it's immune to Ghost and outplaces Girafarig, you should either run a SubCM or an Assault Vest one. other mons that help a lot are Fighting and Fairy types, to counter Dark types that might sweep your entire team, So ScarfGarde does a great job with Psychic, MoonBlast, Trick and Healing Wish, Memento, WoW, DBond or even Focus Blast. Medicham Mega is also a good option, but since you're not playing Smogon's rules you can use powerful and banned threats such as Metagross Mega or Gallade [:\
For a solid defensive core you might want to try Slowbro/Meloetta/Jirachi (or Mew) , that works very well. And for Offense you can use Scarf or Band Victini, but you might want to change Brick Break for UTurn or a Special move to break some defensive monsters (i.e Grass Knot for Quagsire, Fusion Thunderbolt for Slowbros,, etc.). Any of the physicall megas are powerful enough to fit the role.
Ugh, the last thing... DeoD and DeoS do an amazing hazards job, so does Azelf, but I think it's not really that worth it when you can use a psychic uber mon in your team, since there are some good stuff to abuse, such as Sash Deoxys A, Mewtwo, Lugia or even Arceus!, so it's your choise... but you can either use Azelf, Mew (which can Defog too) or a weird Metagross set with Stealth Rock... :]
Oh!, and please, don't use that Sigilyph Smogon set, it's just not good, it does nothing to a pokemon with encore, gets walled by Dark pokemons, and is super hard to set up with since there are plenty of fire types and knock off users in the meta.
And you can always get critted....