On Sephy: To be clear, I'm definitely one of those who turn their nose up at his damage. You can easily have 10-14 materia slots per character endgame, and you only need so many spell damage materia. Thus, not using *at least* 2 HP Plus strikes me as weird, and I often had enough irrelevant slots that I just tossed in some extra +10% lvl. 1 HP Plus materia that'd split off from masters because why not. Ubering your HP is the easiest and most intuitive way to make your party better, and it's storebought, so uh yeah. I had 8,000+ HP on everyone no problem. And back row, of course (Long Range on a physical beater isn't a problem by endgame). So Sephy's physical is merely okay, and Shadow Flare is 70% PCHP or so.
On the bright side, I also assume you basically charge Sephiroth outright and don't have much in the way of ultimate weaponry or super-broken materia (like mastered Double Cut being Quad Cut), so Seph's HP is pretty good to me. In some ways the durability is more important than the damage, because that gives Sephiroth the time to Fly->Supernova, or even just Wall. Important against, say, PCs faster than him who can't 2HKO him.
While posting, might as well do at least one division...
Light:
(Gogo (FF6) - Okay, I'll minorly rant here. Gogo should be reranked to Heavy. Thinking as a voter for a moment, if I see Gogo ranked in Light, the obvious assumption is that he has no skills. If he was in Heavy, then skills are legal. While I prefer Gogo with skills, I already defer to DL interpretations on some characters for the sake of consistency, and thus if he's in Light I'd vote on skilless Gogo, as massive interp splits are no fun - Gogo in Middle would entirely be a "how do you vote Gogo" deal for example, and I wouldn't want Gogo to upgrade that way. Ugh. Just, skilless Gogo is... why even bother ranking him? It's not true to the game and he (she?) is a completely boring dueler this way. Even with just Tools/ Runic / Slots Gogo's interesting, and I think I'd let him have the full suite. Well, with the usual asterisk that Rage would just be Gau's starting Rages, but that's a whole different interp question.)
1. Sten (BoF2)
2. Joker (S3) - Is sorta okay for Light.
3. Tempest (Lunar:SSSC) - Blah.
4. Garcia (FE8) - He can double enemies in FE8 fine! Not really in the DL. Still not terrible regardless.
5. Melody Vilente (WA3) - Don't really respect her barrier much, as think I'd force her to use her later form.
6. Gares (OB) - Is very thankful his earlygame boss form exists (before Princesses / storebought Tarots / uberbroken PCs), as his endgame form would bottom the list.
7. Reis Dular (FFT) - Is a weird healer-buster who isn't good at it?
8. Malak Galthana (FFT) - Weird spoiler? I guess?
9. Lucied (WAs) - Needs durability.
10. Gogo - See above, he SHOULD be #1 but in Light I'd probably vote him sans skills.
A few Suikoscrubs I technically could vote on but didn't really use left off (Hervey, Tai Ho) because darned if I can figure out what they'd be like endgame.