She's a support character designed for solo lanes and built around ramping up AP. Which is to say she falls pretty **** far outside the current meta. Rabaddon's Death Cap is literally the single best all-around item in the game for her and has natural synergy with her passive to such an extent that you can reasonably cut one or two items from what would normally compose your atypical AP carry's item build.

Not to say she's bad in a duo lane, but she's fundamentally not built to make the eurolane (IE: a support and a ranged AD carry) work.

She's actually amazin to counter the current meta, get her and the tank bot (especially singed) and they'll deny EVERYTHING. You need at least 1 mobile tanky fighter in your team to be efficient, Udyr, Trundle, Lee Sin, Singed, etc all work, they'll make spirit bomb actually useful and the shield will reach peak utility then. So yeah... She's VERY situationnal, if you're a support player, she's a great addition to your arsenal but don't expect to main her... Except if you want to solotop or mid often.

That's the thing though. I ward heaps, get oracles, do all the supporty stuff. And still after that i manage to get enough gold to get aegis and wota/ starks or whatever, without adversely affecting the team. why? there is always that cs that your team misses, maybe while the ad carry is backign for items or a lane is pushed and needs to be cleared without the team returning from the enemy base.
So, usually, im not affecting my ad carry's farm much at all, at least, not as much as kayle support :P

you should not get aegis or starks as it doesn't help u at all. She's strongest when building a ridiculous amount of AP... Her heal is a % of max based heal, her shield is OP and explodes and you can't run away when anchored. But she's hard to fit in the current meta though.

But if you find a team that knows what karma can do, you're mostly up for a won game.

Ridiculous amount of ap means gg your teams farm. You don't need to have heaps of ap to be good, as far as i've seen. I find that between my passive and a morello's, deathcap, or dual wota (i only get wota with champions that usually need it and buy it themselves) i get enough ap.
Also, starks is ridiculously good for your ad champs. It's been changed/ replaced now but it could still be good. the reason why i get aegis and starks and stuff is because of what i mentioned before; the only thing she doesn't bring to her team is buffs, getting these items negates that.

Rediculous amount of AP means you were solo mid, so hardly 'gg your team's farm'.

How are you getting a Morello's and a Deathcap as a support, while still getting aegis and starks? Are you 'gging' your carry's farm?

And yes, buying Aegis/other aura items means she brings auras to a team. But a Taric with the same items brings way more to the table.

I get the feeling here that you aren't looking for anything more than justification for using her as a support. The only time she is actually good as a support pick is in a melee-heavy team (no better than other support choices, but she can actually work as the support in a team like that). However, melee-heavy teams have the disadvantage of being melee-heavy...

Good, glad I am not the only one who came to this conclusion.

She is hard to place in most teams because she goes against the meta. She should be chosen when you need a support, solo top (or mid), and have 2 or less AP. She needs a solo lane, and should build, more or less, like an AP carry. Why? Because her early game support is horrible.

If done right, she can carry early and mid game. By the time late game comes around, due to her now high AP and HP, she becomes a great support. The shield adds tankiness to whomever the opponents are focusing, and her heal is AOE AND based off of percent. If you build her AP early/mid game she can easily heal up to 15-19% of missing health. A respectable amount.

Think of it this way man.

Karma is a mage.

Problem solved. She's AP mid that turns out to support. Her ability to make a bruiser a tank is unmatched because of her shield. Her ability to damage and heal is amazing. She is not support tho. Alistar is a better support and with Karama there he can become an amazing intiator.

Shield and speed him while his ulti is up and watch him just run into an entire team under a turret like a boss while CCing all of them, which allows you to get off all your damage.

Karama is great at poking because of her shield, shield yourself and auto attack + ulti type thing + fan = poke that does good damage while you take no damage.

Karama is a mage tho, never forget that. She is a short range mage that excelles with high CC comps. She also allows the jungle to be a squishy champion and still stay effective (I'm looking at your Shaco) in team fights.

Karama is amazing but as a mid AP, not as a bot support. She has to farm to be able to do anything.

Telling you straight up, Alistar bot support mixed with Karama mid = tons of AoE team healing + Alistar is tanky as hell b/c of her shield.

That's my opionion.

I have to rub against the grain here. The meta of your support doing no farming of their own limits your bottom duo lane substantially... If your carry is willing to share a bit of farm, you can make a pretty nasty lane with some creative combos! I find this works not only with Karma, but Lux, and I've even done it with Fiddlesticks.
"Support" sets in mind the notion you're just there as an extra set of sustain and distraction for your carry. Frankly, most casual players find this boring. I've found that, the opposite role, "supporting" with CONSTANT and damaging and harassment to your enemies can ensure your carry is left unharmed and your lane easier to win.
For Karma specifically, I've had a lot of fun with Tristana and Corki. I don't build straight support items, I get some AP and rune/mastery like I would for a mage. They divebomb in and take minimal damage while we AOE the opposition. Early she can swing a good 400 HP in an area between damage, shield and heal. The same strategy has worked with Tryndamere and Pantheon. I balance levelling Shield and Fans with 1 point in Spirit Bond. Gap-closers + Karma's AOE = Carnage.
I'm not here to argue she outstrips other supports, just to show that, if you want to play a support creatively and a bit more aggressively, she pays off pretty well.

I don't think Karma is a mage.

I don't think Karma is a support.

I don't think Karma is a "mid"..

I think Karma is an AP Tanky DPS much in the same way Mordekaiser and Vlad are.


Justification?

1. Tanky DPS generally lack hard CC... Karma lacks hard CC.

2. Tanky DPS generally have abilities which help them sustain in-lane... Karma has abilities which help her sustain.

3. Tanky DPS generally have SOME ability to burst targets down, while not having the kind of burst you would get out of a pure AP or pure AD champ. Karma is to Annie as Garen is to Tryndamere in terms of damage.

4. Tanky DPS generally require a large amount of farm to be fully effective. Karma needs farm.

5. Tanky DPS's job in a team fight is to:

-Be capable of harassing and lasting through the teamfight without needing to recall. Karma has heal, shield, and is capable of sustaining her mana after early game, while still having enough damage and range to give her team an edge if she harasses.

-Be capable of threatening enemy carries OUT of a teamfight, or peeling enemies OFF your carry when they get caught out of position. All 3 of Karma's abilities help her to do this. (AOE Damage+Heal, Haste/Slow in 1 spell, Spell Shield + AOE damage.)

-Make it difficult for enemies to focus them, whilst simultaneously encouraging them to focus them. Think about your average Tanky DPS here... They provide enough threat (Garen, Morde, Vlad, Sion, etc, etc, etc) that if you DO NOT respond to them, they will kill something... BUT if you DO focus them, they take enough damage to give their carries (Ranged AD/AP burst) time to clean up. So you either focus the Bruisers and die to the carry, or you focus the carry and get punished by the bruiser while you get kited. Again, Karma fulfills this role. She does significant damage and provides threat, while being difficult to kill.

It should be noted here that Karma does well solo-top, and she does well in 2v1 situations, AND she does well against other current tanky DPS top picks, who are mostly melee.

Karma benefits from Health Items, due to her passive... which means she is encouraged to build "tanky".

In my mind, here are some good Karma items:

Abyssal Scepter (AP, MR Reduction, MR)
Morellos Evil Tome (CDR, AP, Mana Regen)
Lich Bane (AP, MR, Mana, Passive)
Rabadons Deathcap (AP + Passive which improves her passive)
Rod of Ages (Health, Mana, AP)
Rylais Crystal Scepter (Health, AP, Passive)
Will of the Ancients (AP, Spell Vamp, Passive)
Hourglass (AP, Armor, Active)
Spirit Visage (Health, MR, CDR)
Sorc Shoes Or Merc Treads or Ionian Boots
Thornmail (Cheap armor if getting focused by AD)

Out of these, there are a few which truly shine on Karma. In no particular order:

Ionian Boots (Sorc shoes give flat MPen, which has bad Synergy with Abyssal Scepter which is MR Reduction)
Rod of Ages (Has everything Karma needs)
Deathcap (Makes your shield bombs REALLY hurt.)
Spirit Visage (Caps your CDR after Ionian boots, and gives HP and MR, as well as a boost to self healing)
Abyssal Scepter (Increases damage even more, and gives a nice chunk of MR)
Thornmail (for Armor/Defense) or
Rylais Crystal Scepter (For damage/Health)

Here's one example build:

http://leaguecraft.com/builder/Karma...40031&level=18

I chose to go 9/0/21 for runes, and I picked up flat AP reds and quints, mana regen yellows, and CDR blues.. But you could just as easily go for 9/21/0 or 0/21/9, and go with Magic Pen reds and other rune options. CDR blues + 9/0/21 is just the easiest math for capping CDR.