Having recently beaten the Elite Four rematches, here is my team:
Swampert - Level 63
Nature: Gentle
Ability: Torrent
-Earthquake
-Stone Edge
-Waterfall
-Rain Dance
Swampert was great due to having the best availability in the game and being able to Mega Evolve. The Physical/Special split did make it less useful in the earlygame than in the originals, but when it got moves like Earthquake and Waterfall, it became a great Pokemon, especially when Mega Evolved.
Gardevoir - Level 60
Nature: Gentle
Ability: Trace
-Draining Kiss
-Psychic
-Thunderbolt
-Calm Mind
Gardevoir made up for its poor physical bulk with a combination of Calm Mind and Draining Kiss, and thanks to having Psychic it could be an offensive threat without setting up. Had a rather slow start, but got much more useful after evolving.
Hariyama - Level 63
Nature: Brave
Ability: Guts
-Earthquake
-Close Combat
-Stone Edge
-Belly Drum
Hariyama was great. Being a traded Pokemon, it leveled up faster than any of my other Pokemon in the earlygame, and helped make up for its poor exp group in the lategame. It was good as a Makuhita and became even better as a Hariyama thanks to its rather early evolution. Having Belly Drum was a somewhat risky strategy but in most cases it had the bulk to take hits even at half HP.
Manectric - Level 59
Nature: Bold
Ability: Lightning Rod
-Thunder Wave
-Thunderbolt
-Thunder
-Flamethrower
Manectric was the most useful of my Pokemon IMO despite being the lowest leveled (not counting Groudon who was just added for when I went to rematch the E4) due to being able to Mega Evolve and cripple pretty much any threat to my team with Thunder Wave. It got off to quite a slow start thanks to having very few Special moves, but eventually proved to be extremely useful.
Skarmory - Level 61
Nature: Bashful
Ability: Sturdy
-Slash
-Steel Wing
-Fly
-Roost
Skarmory flew me everywhere before I got the Eon Flute and while its offensive stats weren't great, it took all of the physical hits that my other Pokemon were unable to. It would have been nice if it got some better moves, but who really uses Skarmory for its offensive capabilities?
Groudon - Level 49
Nature: Quiet
Ability: Drought
-Lave Plume
-Rest
-Stone Edge
-Precipice Blades
Groudon, as I said before, was only added for when I rematched the Elite 4, but was surprisingly useful since the AI was terrible at dealing with Primal Groudon, and its absurdly good stats made up for the level disadvantage. Also, catching this thing was hell.
Honestly, this is probably one of the best teams I've used for a while. I did use the Exp Share, but I was underleveled throughout the game due to skipping some trainers. Despite having a level disadvantage, this team got through most battles with ease, only really having trouble with absurd battles like the one against Primal Groudon. What really made me love this team was that it managed to beat the Elite 4 rematches with a 15+ level disadvantage. I will admit that part of it was due to my experience with doing runs in which I'm extremely underleveled, as well as luck and some healing, but it's a pretty big achievement nonetheless, especially considering the natures, IVs, EVs, and moves of my Pokemon weren't anywhere close to being perfect.
