I know there was a conscious effort to condense the amount of sets Gardevoir had but I think an All-Out Attacker set would be appropriate as well as the 3 attack WoW or 3 attack DBond sets that are frequently being used recently.
I've paired a 4 attack Gardevoir(with T-Bolt over WoW or Dbond) with Musharna and is has been nothing short of sensational for me, having no real hard counters or safe switch-ins while proving a huge special attacking threat to compensate for Musharna's more deliberate setup sweeping. I found T-Bolt to be a great addition not just to deal with common walls and threats like Aloma, Drifblim(the lesser used Shadow Ball variants dont even OHKO without rocks) and Braviary but also because a large amount of the sturdiest special walls in the tier are weak to electric, including Noctowl, Mantine, Articuno, Lapras and the dubiously, yet incredibly prolific Wartortle..which I somehow see at least twice per day.
I feel at least one of the sets should be on site since it otherwise undermines that currently Gardevoir is arguably the greatest special attacker in the tier right now...with only the inferior Kadabra giving it competition...however Kadabra is renowned for being weaker and dying in one hit unless it carries a Sash which makes it much weaker, and on top of it, it doesn't get Focus Blast which is critical for success.