I disagree with your premise. She does fit into the meta pretty well as a bottom lane support in an aggressive lane.

That said, I really hate what her design stands for, and the way Riot crafted her kit to make her so **** helpless in other lanes by scraping her AP ratios and making her passive useless in solo situations.

As for sunlight, I always thought it'd be interesting to make the ability proc for half damage if she reapplies Sunlight while the debuff is still active. It always sort of bugged me that her passive did literally nothing when she was by herself, and that her kit was designed to combo directly, but her passive could potentially punish her for doing so if her teammates weren't very on the ball.

Every time leona, and karma pop up in conversation I take the time to let people know how there sub par when compared to other champs that do there jobs.

leona is my favorite tank and I like playing her as such, as meta support she melts to quickly then isn't able to stun lock anyone, isn't great jungle, gets whaled on in top, and **** ratios to be played mid. If she could just proc her own passive (even if its %less) then she'd be fine. if not changed entirely

Sounds like that's more a personal issue tbh.

I'm actually not even sure how you manage to draw this conclusion. Yeah, she doesn't CC as hard as nautilus, but still.

Actually they want to kill her teammates because she does **** damage by herself so can be essentially ignored once she has initiated/comboed someone.

Every other tank in the game can deal damage some form of significant burst and/or sustained damage based on build. Leona is just kinda screwed in that department.

Her abilities mechanically synergize in such a way that they beg to/should be used simultaneously/in rapid succession. This leaves her with relatively extreme periods of nothing but autoattacks between cooldowns.

This isn't much different from other tanks, however all of the other tanks either build items that benefit/enhance autoattacks or have passives that cause their autoattacks to interact with other abilities.

Shen gets bonus damage from autoattacks thanks to Ki Strike. Amumu's autoattacks lower the the targets MR meaning his (and allies) abilities hit harder, Cho'Gath's autoattacks apply vorpal spikes which scale off of his AP and apply on hit affects at range, Nautulus autoattacks apply his passive which help him remain in range long enough for his cooldowns to complete, etc.

Leona is just there, being a minor/ignorable nuisance to her target while waiting for cd's to come up. The only way to counteract this is to build AD, but doing that is counter to the fact that all of her abilities scale of AP.

She needs either her passive or better yet, Zenith Blade to grant a passive magic damage on hit (with AP scaling) in addition to the active. That way she's not just annoying her opponents by tickling them with a sword shaped feather.

Well now, we can compare all the other tanks sustained damage in team fights besides initiation and CC. Blitzcrank gets a constant Static Field. Alistar and his Trample passive deals constant damage around him with each spell. Shen's Ki Strike, Cho'gath spikes, Nasus circle of flame, Amumu pool and MRes de-buff passive. Only one without sustained, constant damage here is Nautilus, but heck, he has one hell of a good burst for a tank. Leona? Damage in short bursts. But only about 33% as strong as Nautilus' burst. A real problem here.

She can ONLY fit into the bottom lane aggressive support role because she simply can't play any other role. She's mediocre at the job anyways, Blitz and Naut do better.

She's meant to be a pure tank, considering what Riot labeled her as (though they do get wacky with labels...). But her skill-set consists of tanking abilities and spells involve initiation and CC. In the current meta, she can ONLY be support-tank because she simply can't solo top, nor clear the jungle fast enough. And as a support, she is considered "aggresive support", the unconventional type such as Blitzcrank, Nautilus, and Alistar to some degree. But Leona does a poor job in this compared to them. Blitzcrank and Nautilus have infinite zoning as far as anyone is aware because of their devastating pulls. Alistar may have to go up himself, but is able to knock-back people into the laning partner AD ranged. Leona? She charges up to them directly, dealing rather mediocre damage, and putting the enemy AD ranged in no real danger whatsoever, because she is in their territory, unlike the Blitz and Naut pulls which pull the enemy into their own territory without really endangering themselves. If they want her to only be tanky (which I do play her as, not full tank; I prefer to have another full tank solo top like Shen or Volibear), she needs to have her CC and/or damage buffed. Heck, a Soraka or Sona can deal more damage than her with the same AP after a certain threshold, a number that I cannot recall currently but is comparatively low.
Btw, I build Leona as tanky AP support with Randuin's Omen, Abyssal Scepter, Mercury Treads, Rod of Ages, Rylai's Crystal Scepter, Shurelia's Reverie, Morello's Evil Tome, etc. The build can really vary depending on what happens and who I'm against, and occasionally, if me and my laning partner and entire team are doing quite well, I get one of the snowball items (Mejai's Soulstealer or Leviathan, Mejai's if I'm going for a bit more damage and Leviathan if I'm not planning to get Warmogs for health).

True, I forgot to mention, but it's a only a slight advantage in the laning phase, and Leona's laning phase is only mediocre at the moment for an aggressive support. I wish to keep the pass-through minions aspect of the spell because it's very unique. Leona just needs a bit more "omph" to her spells to make her a real danger late game.

Well put.

Nice post, detailed and acurrate info on Leonas weakness.

She is "decent" in early game at being agresive, but in mid late game she fall behind, being played as support (no cs, gold items, ward the map) she becames so weak in late game being several levels lower than the enemy team, and being a melee she will fall to quickly in team fights. With a good item build she can be more usefull, but in the current meta way she is played she jsut fall behind to fast.

Agreed. She's an example of a champion where they were like:

"Hmmm this champion is extremely tanky, and has some of the longest CC in LoL, so we're giving him/her incredibly low damage."

And then they realize points 1 and 2 are false, so you have this champ thats mediocre in both categories, with low damage.

She isnt called just "pure tank" she's called "the only pure tank"

I really feel Leona's passive should proc extra effects from her abilities as well as damage, since she combos them together so much. Should make up a little for her lackluster damage. For example, shield of daybreak will deal 30% more damage, eclipse heals her a little for the amount of sunlight targets hit, and zenith blade now snares for twice the duration. Her ultimate could also blind the targets (Like grave's smokescreen) due to excessive sunlight. Also works on Lee sin.

Leona was the third champion I purchased, and never a purchase I regret, because I have so much fun playing her. On the other hand, it's very much a drag to be pinned to one role because you're bad at everything else, and then to not even be particularly strong at that role.

I am going to disagree with letting Leona proc her own passive if it's for less damage, for a somewhat non-obvious reason. If she's balanced around her own damage, Sunlight does too much when her teammates proc it. If it's balanced around her teammates, you're stealing damage from them as a direct consequence of trying to do your job (E+Q+W combo, say) and lock a player down.