Brandonjmatt - I am not particularly interested in your testing results. I didn't say this was the best version of Gardevoir out. Read the first paragraph of my first post. I didn't say it was the best deck in the format, either. Have a question? Have a comment on the deck? Then post it. I don't need advice unless it's good advice. Thanks.
WeileMom - Well, it's all a matter of opinion, really. Gardevoir has just been fighting an uphill battle ever since the gigantic metagame shift after EX: Team Rocket Returns was released. Dark Dragonite decks plain outspeed Gardevoir. Dark Dragonite is the fastest deck with multiple copies of Stage 2 Pokemon in it in this format. Gardevoir really only stood a chance, and a small one at that, against Blaziken in Eon because Blaziken wasn't that fast a deck until you got the setup in motion. Dark Dragonite has better startup time because of Dark Electrode' Darkness Navigation and Dark Dragonair's Evolutionary Light. Blaziken needed the Dunsparce setup, and Dragonite relies on it much less so.
The other leading deck in the format, and quite possibly the best, is Dark Tyranitar/Dark Ampharos. Gardevoir's Psy Shadow damage, along with the ATM: Rock, then Sand Damage, then Dark Impulse combination, is too much for Gardevoir to handle. Running a pokemon like Milotic doesn't fix this problem. The Milotic will die instantly thanks to the above combination, with some help from Rocket's Tricky Gym if necessary. The fact that Dark Tyranitar/Dark Ampharos decks can run with only 1 energy on their side of the field doesn't exactly help out Gardevoir's situation either. It makes Psystorm almost impossible to OHKO with, and the lack of OHKOs means that Mr. Briney's Compassion can be used to heal up TTar. TTar has more HP than any non-ex pokemon in Gardevoir decks, and TTar/Amphy wins the prize battle (Gex gives up two prizes, everything in TTarAmphy gives up one).
It's just not tournament-caliber. The metagame is against it. If you want to win, you have to metagame. Playing one of the above two decks is the best way to go, unless you can metagame sufficiently so that you can play another deck at optimum performance in your specific environment.
As for the "won't ever be again" part, the format isn't shifting for quite some time (confirmed by Nintendo; the format isn't changing until after Worlds 2005). This means that Dark decks are most likely going to continue to dominate the format until we get there, and then Gardevoir will be rotated out of the format, sealing its fate.