Rotom's regular form is mediocre because Raikou, Mega Manectric, and Gengar do its roles better. The best form to use it with is the Wash form. In both X/Y and OR/AS, Rotom's form can be changed by interacting with a set of cardboard boxes that contain various electrical appliances in the professor's lab. Wash Rotom is the best Rotom form to use because it only has a single weakness to Grass, an uncommon attacking type. It also counters Talonflame, a top threat, very well:
-Volt Switch
-Hydro Pump
-Will-o-Wisp
-Pain Split/Rest
Nature: Bold
EVs: 248 HP/252 Def/8 Spe
Item: Leftovers/Chesto Berry
Porygon is the lowest form in its evolutionary line. Evolve it into Porygon2. As weird as this sounds, it's not worth evolving all the way to Porygon-Z because Porygon2 is bulkier, especially when it's equipped with Eviolite, even though you need to be wary of Knock Off. Porygon-Z struggles in standard play because while its Speed isn't bad, it isn't good either, and it's also frail:
-Ice Beam
-Thunderbolt
-Toxic/Thunder Wave
-Recover
Nature: Calm
EVs: 248 HP/204 Def/56 SDef
Item: Eviolite
Ability: Trace
Eelektross is badly outclassed by other Electric Pokemon, like the above Electrics I mentioned, as well as Mega Ampharos. It isn't too bulky, and it's very slow. While Mega Ampharos is also slower than Eelektross, it's also more bulkier. However, I won't suggest Ampharos here, as Therian Landorus should replace Eelektross. It provides Stealth Rock support for the team, as well as U-turn to synergize with Wash Rotom's Volt Switch. Even though both moves force the user out of battle, this is advantageous, as when the opponent switches to something else as you U-turn/Volt Switch, you can respond by switching to a check/counter. U-turn and Volt Switch also are good ways to get frail attackers into battle unscathed if the user happens to be slower than the target, as normal switching will make the new Pokemon open to an attack:
Therian Landorus:
-Stealth Rock
-Earthquake
-Stone Edge/Rock Slide/Knock Off
-U-turn
Nature: Impish
EVs: 252 HP/240 Def/8 SDef/8 Spe
Item: Leftovers/Rocky Helmet
or
-Stealth Rock
-Earthquake
-Stone Edge/Knock Off
-U-turn
Nature: Adamant/Jolly
EVs: 72 HP/252 Atk/184 Spe
Item: Soft Sand/Earth Plate/Focus Sash
Blastoise and Gardevoir are only worth it as their Mega Evolutions, but you'll need to pick one out of the two. Both of your current sets also waste away their abilities, Mega Launcher and Pixilate, respectively. The former powers up aura- and pulse-based moves, while the latter turns Normal moves into Fairy ones and powers them up. Pixilate also won't affect moves that are already Fairy type, like Moonblast. Given Gardevoir's Steel weakness, it needs Focus Blast to be able to damage Steel Pokemon, as your current set is walled by them:
Blastoise:
-Hydro Pump/Scald
-Dark Pulse
-Aura Sphere/Ice Beam
-Rapid Spin/Ice Beam
Nature: Modest
EVs: 236 HP/252 SAtk/20 Spe
Item: Blastoisinite
Gardevoir:
-Psyshock
-Hyper Voice
-Focus Blast
-Taunt/Will-o-Wisp/Calm Mind
Nature: Timid/Modest
EVs: 24 Def/232 SAtk/252 Spe
Item: Gardevoirite
Ability: Trace
Depending on what Mega you opt for, here are some alternatives:
If you opted for Mega Blastoise:
Sylveon:
-Hyper Voice
-Psyshock
-Shadow Ball/Hidden Power (Fire/Ground)
-Baton Pass
Nature: Modest
EVs: 244 HP/252 SAtk/12 Spe
Item: Choice Specs
Ability: Pixilate
or
-Wish
-Protect
-Hyper Voice
-Heal Bell/Toxic
Nature: Bold
EVs: 252 HP/220 Def/36 SDef
Item: Leftovers
Ability: Pixilate
or
-Calm Mind
-Hyper Voice
-Substitute/Wish
-Baton Pass
Nature: Bold
EVs: 252 HP/240 Def/16 Spe
Item: Leftovers
Ability: Pixilate
Clefable:
-Calm Mind
-Moonblast
-Flamethrower/Thunder Wave
-Soft-Boiled/Moonlight
Nature: Calm
EVs: 252 HP/184 Def/72 SDef
Item: Leftovers
Ability: Magic Guard
or
-Stealth Rock
-Moonblast
-Fire Blast/Thunder Wave
-Soft-Boiled
Nature: Calm
EVs: 252 HP/172 SDef/84 SDef
Item: Leftovers
Ability: Magic Guard
or
-Wish
-Protect
-Moonblast
-Flamethrower/Heal Bell
Nature: Bold
EVs: 248 HP/252 Def/8 SDef
Item: Leftovers
Ability: Unaware
or
-Calm Mind
-Moonblast
-Moonlight/Wish
-Heal Bell/Protect/Flamethrower
Nature: Bold
EVs: 248 HP/252 Def/8 SDef
Item: Leftovers
Ability: Unaware
Alakazam:
-Psychic
-Shadow Ball
-Focus Blast
-Encore/Thunder Wave
Nature: Timid
EVs: 4 HP/252 SAtk/252 Spe
Item: Focus Sash
Ability: Magic Guard
Sylveon and Clefable are excellent support Fairy Pokemon, while Alakazam is a good revenge killer.
If you opted for Mega Gardevoir:
Gyarados:
-Dragon Dance
-Waterfall
-Bounce
-Substitute/Taunt
Nature: Adamant/Jolly
EVs: 88 HP/220 Atk/4 Def/196 Spe
Item: Leftovers
Ability: Intimidate
Azumarill:
-Waterfall
-Aqua Jet
-Play Rough
-Knock Off/Superpower
Nature: Adamant
EVs: 172 HP/252 Atk/84 Spe (Choice Band) or 240 HP/252 Atk/16 SDef (Assault Vest)
Item: Choice Band/Assault Vest
Abiilty: Huge Power
or
-Belly Drum
-Aqua Jet
-Play Rough
-Knock Off
Nature: Adamant
EVs: 92 HP/252 Atk/164 Spe
Item: Sitrus Berry
Ability: Huge Power
Feraligatr:
-Dragon Dance
-Waterfall
-Crunch/Ice Punch
-Superpower/Ice Punch
Nature: Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Life Orb
Ability: Sheer Force
or
-Swords Dance
-Waterfall/Aqua Jet
-Aqua Jet/Ice Punch
-Crunch/Superpower
Nature: Adamant
EVs: 144 HP/252 Atk/112 Spe
Item: Life Orb
Ability: Sheer Force
Starmie:
-Hydro Pump
-Psyshock/Thunderbolt
-Ice Beam/Hidden Power (Fire)
-Rapid Spin/Recover
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Ability: Natural Cure/Analytic
or
-Scald
-Psyshock/Reflect Type
-Rapid Spin
-Recover
Nature: Timid
EVs: 248 HP/8 Def/252 Spe
Item: Leftovers
Ability: Natural Cure
Gyarados, Feraligatr, and Azumarill are powerful physical attackers, while Starmie provides a specially-based alternative. While the last set seems out of place, Starmie does it well, as this lets it beat its counters by copying their types, namely Bisharp, Ferrothorn, and Tyranitar