Leblancs early game is brutally overpowered. She will kill you, and there is nothing that can be done about it.
Her mid game is ok, she can make lots of kills but can't farm.
She might have the worst late game out of any champion. She can't farm at this point, and she needs lucky positioning to kill anything.
Trying to improve leblancs late game without drastic changes isn't going to work. She's still going to be one of the worst champions in the game, because it is very, very hard to win before 20 minutes.
Her lategame is fine. If the adc/ap/support doesn't build anything to survive with you can still 100-0 burst any three of those champions in most cases. And then come back in about 10 seconds later and nuke someone else for ~800+ damage.
http://oi41.tinypic.com/9ht4ea.jpg No matter which way you slice it you'll both be ending up in Hell!