All right, trying to come up with some team configurations. Most of it's gonna come from testing, but here's the Pokémon I have (or still want to breed). Anyone see any potential here?
There's more, but I'm tired of breeding for a while. I want to beat White and HeartGold.
I never play outside of the BattleSpot, and always doubles, so I don't know if multiple Pokemon with mega stones will work. I think only 1 pokemon can mega-evolve per battle, so while you can send them out, they will not be able to mega evolve if you've already mega evolved one during the battle already.
I'll just suggest what I feel comfortable suggesting, it may not fit your whole team, but it may help out the individual pokemon. This is also probably more adviced geared towards double battles.
In your first team:
Arcanine should have Intimidate, he's fairly weak, and no one is going to hit him with a fire move unless it's on the switch, which will basically be a one-trick thing if you're opponent is unawares.
Dragonite with multiscale is badass, and I have one on my team, but with Dragon Dance, Earthquake, Extremespeed and Dragon Claw, holding Weakness Policy. Weakness Policy takes advantage of multiscale, but can hurt you if sand or hail is out, because it'll end up being useless unless you're hit by a burned Pokemon or a weak Supereffective move. Outrage locks you in and leaves you vulnerable once you've been hit once. Extremespeed is necessary IMO because Dragonite can survive a SE hit and be powered-up with Weakness Policy, and do pretty dang good damage with Extremespeed without worrying about being outsped, and probably sweep if it got off a DD. I'd choose either Fire or Thunderpunch, but not both. EQ is my choice of other move but honestly I rarely get to use it so I may swap it out for FP or TP.
I'm not a huge fan of Mixed Garchomp on your next set. Focus on Attack or SpAttack, don't mix em. I'd get rid of mega and go Rocky Helmet. Back when Diamond and Pearl came out I had Substitute/EQ/Dragon Claw Jollychomp which was nice. For a fourth move I used Poison Jab for Fairy Coverage but I don't really like Garchomp anymore so I don't use him for some reason.
Anyway just my 2 cents but I like your teams, they aren't overused by any means and look like fun!