Surf and Hydro Pump is super-redundant. I'd say stick with Surf, it's slightly weaker, but has way better accuracy as well as higher usefulness in double battles. Or you could go for Water Pledge if you use it together with Meganium, though that would be very rarely viable. Your call.
Regarding moves, I'd say you should go back to E12 or E11, catche a male Remoraid, level it till it gets Ice Beam and breed that with a female Greninja (use Ditto first if it's male). But don't go to E10 or earlier with Greninja, gen 6 stuff wasn't implemented back then.
Other than that, Hidden Power and Grass Knot are viable moves as well, and Spikes can be used to get a free turn on predicted Electric attacks, but that's the only time you should use that over any attacking move. You could also get a new Froakie and get it Bounce via level-up before the final evolution into Greninja.
If you get a new one and hold off on evolution a bit longer, you can get it Extrasensory via level-up. If you go back to E12 or earlier, you can breed it with a Deerling/Sawsbuck to get Energy Ball on it. Or, since Ninetales Physical Attack and Special Attack are so similar, Flare Blitz is quite good on it as well. But there is no way to get both E.Ball and F.Blitz at the same time in E13. In E12- you need Smeargle.
Also, if you're using Will-O-Wisp, you should use Hex rather than Dark Pulse.
Should you ever have Speed issues, Gardevoir can learn Trick Room, which we have the TM for.
Going back to E12- gets you Thunderbolt from Stunfisk. You have plenty of Ghost/Dark attacks anyways, might as well.
Litwick can also get you Will-O-Wisp.
Get a Mienfoo and a Hitmonchan for Drain Punch and Bullet Punch, Flatter and Cross Chop can go. Also, Poison Touch + Poison Jab has a 44% chance to Poison if you want to switch, but Dry Skin seems better. Also, Dry Skin + Surf is a great combo.
Noivern isn't all that bulky to begin with (not to mention healing item's existence), so I'd say you should get it Boomburst and go stack up on Normal Gems from the Obsidia Department Store.
I'd also recommend Frisk over Infiltrator. Infiltrator is rarely useful anyways and Frisk is not only useful for item hunting, it can also save you from a nasty surprise from a gym leader.
Well, Steelix really isn't all that great, but oh well. Gyro Ball is stronger than Iron Tail while not suffering from any accuracy issues. Fun Fact: Trick Room changes how Speed works, but not the actual stat, so you can go first with TR while maintaining max power Gyro Ball.
Curse is a great move for it, depending on what we face Stealth Rock can be great, Rock Tomb's Speed drop can support your team well.
Again, Healing moves are unnecessary with Healing items. You should go with Reflect and Light Screen. Instead of Poison Powder, you should use either Body Slam (30% para chance), Nature Power (if you fought Florinia in E13) or Leech Seed or Wring Out.
Heracross' best set can be gotten in E12 or earlier. Breed Geodude>Crustle>Heracross for Rock Slide (or Rock Blast) and Earthquake.
Feel free to PM me if you need any help with breeding.