I hope Moores will actually be coming back at some point o.o;
baratron's advice is a very good place to start. By getting rid of your extra attacks of a similar nature (ie. Blaze Kick and Firepunch) and useless HM attacks it'll free up a lot more space to try out new attacks and strategies. Which is where my question comes in: do you own FR/LG or Emerald? If so they could greatly change any moveset advice of mine because of their huge range of learnable attacks.
Instead of full moveset ideas here are some Anti-Elite strategies: Dragon Dance can be very useful ingame because you can use it a few times to boost your Attack/Speed, heal, and then bash away your opponent. Gyarados learns it at level 50, and Altaria at level 40. For Altaria the speed boost alone may be worth it, but Dragon Dance on Gyarados can be devastating if you pull it off right. It's already super powerful, and by raising that already high attack and its Speed you'll be able to take out most anything. Earthquake (EQ) is a perfect attack for a Gyarados like this but your Aggron got your only EQ TM, eh? Either way, baratron was right in saying that Gyarados is generally a better Attacker than Special Attacker.
Your Blaziken needs a stronger Fighting Attack. If Level 59 for Sky Uppercut is too far off teach it Brick Break. Double Kick is good enough for most things but the added power of Brick Break is very useful to have. With Brick Break in tow Blaziken will be able to take out all of Sidney's Pokemon and Steven's Cradily easily. Blaziken is also your Metagross killer. One good Flamethrower/Blaze Kick should KO it if your level is high enough. If Metagross hits you first with Psychic and KO's Blaziken, though, send out your Groudon and use Fireblast. And yeah... I perfer Flamethrower to all other Fire attacks for its high power and great accuracy.
Steven's other Pokemon vary. EQ or a Water attack can take out Aggron, Flamethrower or an Electric Attack can get Skarmory, Claydol can be beat by pretty much anything that it's not resistant too (just keep bashing it), and Armaldo is weak against Steel/Water attacks.
An Anti-Dragon Pokemon could be very helpful, or at least something with Ice Beam. That'll take out Salamence and the Flygon's quite easily. Altaria can learn it, and (considering that you don't plan to catch a new Pokemon for Icebeam) while it is weak against Drake's Pokemon it should be able to survive a Dragon Claw from Shellgon to beef its speed up with Dragon Dance. After that you'll be able to hit Flygon/Salamence/Altaria before they can get you.
If you have a Thunder Bolt TM handy Gardevior may be a good candidate for it - great for taking on Glacia. With Psychic, Calm Mind, and T-Bolt, Gardie can be an incredibly great Pokemon to have around. Use Calm Mind a few times and then bash away your opponent. With its already high Special Attack and Special Defense you'll only have to fear powerful physical attackers.
Speaking of Glacia... Your Blaziken could do some damage to her. Flamethrower the Glalie's. After that, switch in Gardie with T-Bolt to finish her off. Fighting Attacks would also be very effective against Seoleo/Walrein's Ice-traits but Blaziken might not survive the Surf attacks.
That leaves Phoebe... I'm sure your Groudon or any other powerful Pokemon can deal with her. Since I don't think any of your Pokemon can learn Shadow Ball just do your best to beat her down.
In the end beating the Elite 4 may simply come down to leveling up your team. Some people find it useful to be around level 50. Couldn't hurt.
