I actually use a Gardevoir non-mega in Ubers as a special tank. I have yet to drop below 1700 using her, and it really makes a mind game when pairing with Lucario as to who is the mega. This is mine
Wall Breaker:
Gardevoir (F) @ Leftovers
Ability: Trace
EVs: 200 SAtk / 56 HP / 56 SpD / 200 Spd
Timid Nature
- Moonblast
- Psyshock
- Thunderbolt
- Protect/Will O' Wisp
Now of course, everyone is laughing at me, but seriously, it's a viable if not really good set. Tracing Flash Fire on Heatran or Water Absorb on Jellicent is gorgeous, and sponges an attack. I trace Protean on Greninja, and have yet to lose to one. I'll use Gardevoir to sponge status and switch in on a Blissey-- with Psyshock dealing nice damage back. Yes, it's true this set can't take physical hits, but that's what the other five slots on the team are for. Why try to make Gardevoir compensate for something it just can't do instead of enhancing what it really can? No matter how many defensive EV and IV you put into it, Aegislash, Scizor and Cloyster will nail it to the ground. Instead, I use Gardevoir to beat the walls. I don't find Mega Gardevoir to be overwhelming or worth my mega-spot, no matter how much I love her. Instead, I use her as a standard-- which works really well in her niche. Sure, she will go UU, but she'll go UU with a non-mega set as well.
EDIT: I mention in this Lucario. With Lucario being Suspect Tested, I will mention other Mega-evo's it works well with. Lucario, Venusaur, Alakazam (though you have to watch the double psychic on this one, I find that having two trace options is hilarious. Just for kicks I added a Porygon 2, and had Triple Trace.), Gyarados, Scizor, Tyranitar and Garchomp.
Repeat: all of these pokemon, when paired can allow for a Mega-Mind Game. That is, you can choose which you want to be a mega, and which you won't. Unexpirienced Gardevoir facers will only expect the Mega-Gardevoir, and prep as such; so a different Mega works really well with the above set.