Hypnosis + Dream Eater is rather risky combo. I might even say pointlessly. So no, it isn't.
- Hypnosis has pretty bad accuracy, and if it misses then your Gardevoir has a missed a turn. Meaning it may have to take a hit, and we all know how that ends with 68 HP and 65 defense.
- Even if Hypnosis hits, your opponent may just switch out that particular Pokemon for something else. So if you used Dream Eater then your plan would fail, and that Pokemon will get a free switch-in.
- Taunt-bait: You have just two attacking moves, and one of them is dependent on Hypnosis to work. So you are left with just Psychic then. Encore, while not as common, can catch you on a set up move and screw you over.
- Completely walled by a Dark type. Something as frail as a Weavile can halt this Gardevoir without being afraid of a Fairy move.
Yeah, normal Gardevoir outclasses this one. Even if you managed to work it, you will require quite a lot of support and predictions. No Pokemon should be worth that much of a head-ache in a team, otherwise without it the team falls apart.
Hope I helped!