EDIT 2:
I'VE HAD MY FIRST EVER NUZLOCKE VICTORY!
Here's my E4/Championship team:
Sean the Exploud, level 52 (Return, Fire Blast, Hyper Beam, Shadow Ball)
[Died vs. Steven]
Gloria the Manectric, level 51 (Thunderbolt, Bite, Thunder, Protect)
Daniel the Gyarados, level 51 (Earthquake, Dragon Dance, Thrash, Hyper Beam)
[Died vs. Steven]
Porky the Grumpig, level 52 (Psybeam, Psychic, Calm Mind, Confuse Ray)
Magellaen the Tenatcruel, level 52 (Surf, Acid, Barrier, Ice Beam)
Alabaster the Absol, level 51 (Aerial Ace, Bite, Iron Tail, Perish Song)
[Died vs. Steven]
The entire team made it to Steven alive. I used a little bit of everyone against Sidney (except Porky). Magellaen beat Mightyena; Alabaster beat Shiftry; Sean beat Cacturne, Daniel beat Absol, and Gloria beat Sharpedo. Easy as pie.
Sean was able to sweep Phoebe with Shadow Ball.
Porky was able to sweep Glacia (Calm Mind x6 against her opening Glalie, and then 1 Psychic attack took out her entire team from there).
Magellaen was able to sweep Drake. Barriers + Ice Beams + occasional Full Restores. And I was impressed that I was able to sweep three consecutive Elite 4 members with one pokemon each.
I was not able to sweep Steven, though; nor did my entire team emerge unscathed. I opened with Daniel against his Skarmory. Dragon Dance x6 (while occasionally Full Restoring against Toxic). He ended up switching Skarmory out, and Daniel was able to sweep Cradilly, Claydol, and Armaldo. Unfortunately, Daniel fell to Aggron when I forgot to use a Full Restore after it was confused from Thrash.
After that, I bought out Sean who proceeded to MISS THREE FIRE BLASTS IN A ROW. I ended up hitting it with 2 Fire Blasts, but it was not able to kill the Aggron, and Sean fell in battle, as well.
Magellaen came in for the revenge kill with Surf, and that brought Skarmory back out. Gloria was able to make short work of the steel bird. Then came the Metagross, and I was feeling bad. My Earthquake user and my Fire Blast user were both dead. But luckily I came prepared with a backup plan! I sent out Alabaster to use Perish Song opening turn. Metagross responded with Meteor Mash, shuffling off Alabaster's mortal coil. Still, his sacrifice will never be forgotten, because he gave me the means to finish off Metagross. With Perish Song counting down, I sent out Gloria who proceeded to Protect herself from Earthquake for 2 turns in a row (Woo! Lucky double Protect!). With only one turn left on the Perish Song, I switched out to Porky who easily survived Metagross' last Earthquake attempt. The Song claimed its victim, and I was victorious!