Heliolisk (F) @ Leftovers
Ability: Dry Skin
EVs: 68 SAtk / 252 SDef / 188 Spd
Calm Nature (+SDef -Atk)
- Rain Dance
- Psych Up
Dry Skin + Rain Dance + Leftovers is the best combo on Heliolisk, imho. With the Rain set up I can heal off most of the Sub damage. This set can wall pretty much any special sweeper with a SE move, though probably not any Megas or Legends. But she walls pretty well.
EVs highlight Special Defense and Speed. 301 speed is enough to outspeed the bulkier sweepers and lets me catch a few already-fast-and-not-investing-in-speed-evs sweepers. Otherwise Heliolisk can usually tank a hit before setting up a Sub.
Once I have a Sub up, I have one free turn to do as I please. I usually set up Rain Dance ASAP, since the recovery is amazing on Heliolisk due to her low HP.
Thunder wrecks in the Rain, having a whopping 165 base power after STAB. It's the strongest Electric type attack and this set only works in the Rain so why not.
Psych Up is probably a questionable move, but I just picked it and it worked. It works well against Pokemon like Gardevoir (non-Mega), who set up with Calm Mind first. One time a dude got like +3 SAtk and SDef on a Gardevoir. I was faster, so I was able to Psych Up and tank the blow, then proceed to damage the Gardevoir like there were no stat changes (due him being +3 SDef and me being +3 SAtk).
The problem with this set is of course the Ground type, Megas/Legends, anything that resists Electric and Physical or Mixed sweepers. I keep this set away from such things, and it works pretty well. Not the best set on Heliolisk but a good one if you ask me.