Replace Moonblast with Wish, Hyper Beam to Hyper Voice, Psyshock to Mystical Fire, and Yawn to Protect, if you were to ask me.
Technically, the eeveelutions that have the best offensive stats are Espeon and Jolteon, with Espeon having 130 base Special Attack and 110 base Speed and Jolteon having 110 base Special Attack and 130 base Speed. While both certainly have good stats, Sylveon is arguably the best eeveelution as far as competitive play goes, since Pixilate is and amazing niche.
Sylveon @ Pixie Plate
Ability: Pixilate
EVs: 252 HP / 252 SpA / 4 SpD
Modest Nature
IVs: 0 Atk
- Wish
- Protect
- Mystical Fire
- Hyper Voice
As for Espeon and Jolteon, if you want to use them, here's what I recommend:
Jolteon @ Choice Specs
Ability: Volt Absorb
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Shadow Ball
- Thunderbolt
- Volt Switch
- Hyper Voice
Espeon @ Leftovers
Ability: Magic Bounce
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Calm Mind
- Psyshock
- Dazzling Gleam
- Shadow Ball
Hope this helps! :)