First of, Heracross reKs Luna with his STABs and Moxie.
It has 110 Base Special Attack! And Pixilate! And you can set it up to fire off a 390 BP move, a trick only it and Mega Glalie's Refrigirate Explosion can pull off!
You don't even have to breed it to make it good (sorta don't). But you have to keep it as an Eevee until 45 to get it Trump Card.
See, Trump Card gets stronger the less uses it has left, it goes 40, 50, 60, 80 and 100 BP if you have 5+,4,3,2 and 1 use left. But Pixilate multiplies a Normal moves power by 1.3 and makes it a Fairy move which then gets a 1.5 STAB multiplier. So Trump Card actually has 78, 97.5, 117, 156 and 390 BP!
Moves to go with it would be Shadow Ball, Light Screen or Hidden Power and Moonblast (to have a stable attack).
Oh, and no Wish. That's a competitive move, to be used in a competitive environment because healing items aren't available. We have healing items.
Anyways, looking at the rest of your team, Swoobat, Simipour, Tauros and Liepard could and should go. A few gyms from now (dunno if you can do this before or after E14's gym) you can get yourself a Toxic Orb and utilize Guts Luxray which is best Luxray. I'd wait and give that a shot, but if you don't want it anyways, that's 5 team members to be replaced.
Now, 2 things I see are that you 1)dislike breeding, so I'll keep that in mind with my suggestions; and 2)want to have a tank somewhere. Now, you don't need one. There is no need for any "roles" at all. I've got an all-out attacking team and am doing just fine. But nonetheless, if you insist, Sylveon, especially with Light Screen is a wonderful special tank, and I guess I'll add some other ones you could use down there vvv:
Now, team members. We've already got your Delphox (for which Flame Charge would be an excellent move) and Sylveon. Let's look at their (in my opinion) optimal sets: Delphox
Timid/Modest
Magician
Flame Charge/Light Screen or Will-o-Wisp
Shadow Ball/Hidden Power
Psychic/Psyshock
Flamethrower
and
Sylveon
Modest/Sassy
Pixilate
Trump Card
Moonblast
Light Screen
Shadow Ball/Hidden Power
We're past the Psychic and Ghost gyms, so you could use some HP instead of Shadow Ball.
For the third member, my go-to recommendation for everyone is Durant. It's fast, it has great base defense and a Steel typing, and the Hustle ability essentially gives it 190 Base Attack. I'd recommend breeding it with a Dwebble (will be reached soon after Luna) to get it Rock Slide or a Skorupi for Hone Claws to make this thing even more of a monster, but you said you don't wanna breed, so go with:
Durant
Jolly/Adamant
Hustle
X-Scissor
Iron Head
Dig
Crunch/Retaliate (Retaliate is in the game corner and online Voltorb calcs do exist, if the game troubles you)
As for a good number 4, I'd go with a Tyrantrum, but only if you'll breed for Dragon Dance (Altaria/Horsea) which, believe me, definitely pays off. Seriously, this guy is so good. 1 Dragon Dance + Rock Head + Head Smash spam = Badge get.
Tyrantrum
Adamant/Jolly
Rock Head
Dragon Dance
Earthquake
Head Smash
Dragon Claw
But if you REALLY don't want to breed, go for Archeops (Dragon Claw, Rock Slide, Acrobatics and Endeavor).
Next up, 5th:
Gogoat
Careful
Sap Sipper
Bulk Up
Horn Leech/Leaf Blade
Earthquake Brick Break/Aerial Ace
And for the 6th go for:
Heliolisk
Timid/Modest
Dry Skin
Thunderbolt
Grass Knot (if you have the TM/beat Florinia before E13) or Hidden Power (Ice would be perfect)
Dark Pulse
Surf
....or that's what I'd do. Do tell if you'd rather not use any of these guys and I'll try to see what could replace them.