This is the best coverage you are going to get, and it only works with the DP Skill System. With that, the last two moves here become special attacks. (Mud Bomb: 85 base power 95 accuracy, Ground, lowers Sp.Attack; AeroBlast: 100 base power 95 accuracy, Flying, increased critical hit ratio). EVs are pumped into defence to prevent Patchouli from getting killed by weak physical attacks, especially stupid things like Quick Attack.
If you want, you can pick Bold as the nature to increase physical survivability. You can also take some EVs from special attack to place into HP or Speed, but there isn't much to outspeed except maybe Kanako and Yuyuko.
You can drop FiveElements for Psychic if the PP is an issue. With a Special Attack stat higher than Mewtwo's, it probably doesn't matter much especially if you factor in STAB. You can also dump AeroBlast for Reflect, but it can be hard to use with Patchouli's low speed.
If you're playing hard mode, forget EX Patchouli and go for Final Patchouli: that one can learn Ice Beam, Hydro Pump, Morning Sun, Thunderbolt...