Karma is an "ok" champion
Early game : I find her alright during this time, she has ability to lane, stay in lane, and do not have to worry abut mana problems, as well has the ability to farm.
Meta-game : This is where i thick she excels at, stay with your carry and keep em' killin, and alive.
Late game : I find Karma, weaker than her meta-game, but still able to make the life of a carry much, much more harder to kill.
Overall i found Karma to be an all around well champion, with the ability to excel in a "Pre-made" or a Pre-Arranged team of 5. Since her role is very specific and requires the cooperation of the team to do so (most of the time).
i see alot of "Nuke" builds on her, and see her trying to be played as a Spellcaster; so far i have not seen 1 good Spellcaster/Mage Karma soooooo....