Leblanc is oppressive and unhealthy

Pros to playing Leblanc: Leblanc has an oppressive lane phase. With a simple QW (not difficult to land) she outtrades every single midlaner in the game. She has the mobility to easily avoid skillshots and with 4 seconds on her distortion return she is impossible to gank.

You shut leblanc down by 'not giving her kills' but her level 6 all but guarantees that she kill you due to the absurd mobility and burst from base damage alone. Even safe picks mid such as Orianna who can shield her damage will get bullied out due to her low cooldowns, and that's not even including the zero mana cost on her ultimate.

Once bullied out, which is relatively easy, Leblanc is free to roam where she can easily pick up kills with relative safety due to her mobility. This is especially true in bottom lane where ADCs typically are underleveled and running minimal magic resist due to restricting item builds.

Note: Many argue that her waveclear is poor, but this is simply not true. Depending on the rank, her ultimate is on a 18-30 second cooldown after her first CDR item (Morellonomicon) and she can 1 shot entire minion waves instantly for minimal cost in mana or cooldowns.

"Cons" to playing Leblanc She is supposedly "balanced" via a poor teamfight and a lack of split pushing strength. Personally I don't see how these cons are powerful enough to outweigh the pros listed above, and I will explain why.

"Poor Teamfight" - Leblanc has high damage in an AOE on her distortion, which is generally the first skill she maxes. With morellonomicon at level 9 she can use distortion once every 7.5 seconds and she can mimic that with her R once every 30 seconds for tons of AOE damage. This damage is very reliable due to her mobility and safety and it still leaves her with Q and E for single target damage to assassinate, Q being on an extremely low cooldown with a very high potential for damage.

"Bad Splitpush" - Due to her excellent mobility and waveclear I think it's far from true to say that Leblanc has a bad split push. The only downside to her splitting is lack of tower damage, but with an elixer of sorcery even this is negated due to the passive true damage on auto. Due to her potential to assassinate and her ability to escape threats (generally tanks, which are low damage and non threatening to begin with) Leblanc actually makes for an excellent split pusher with a simple 400 gold purchase.

So that leaves us with one final "con" for Leblanc - her assassination potential falls off heavily in the latest stages of the game. A banshees veil on an ADC/APC renders them far more difficult to kill. This does not, however, detract from her teamfighting or excellent 1v1 capabilities by too large of an extent. In the late game if properly played she isn't much worse for teamfights than a full build Ahri, and she can still easily chunk ADCs/APCs out of a teamfight even if they have the appropriate MR items.

So that's my attempt at calmly calling Leblanc overpowered. I think the small tap to her ult ratios a couple patches back does not even begin to address the problems with this champion. Her low winrate is not indicative of her strength in my opinion and she needs to be addressed.

EDIT: Decided I would add my suggestion to change Leblanc since this thread is getting enough attention. In the past her ult damage scaled off of the number of points she had in a particular skill. This meant that in order for Leblanc to assassinate a target, she had to max her Q first so that the mimic Q would do enough burst damage. Reverting this change would reduce her waveclear or it would force Leblanc players to make a decision for the early-mid game on which style of play to focus. I think it would be a healthy change because it would emphasize a weakness in Leblanc's kit without directly removing her ability to assassinate or the smooth feeling of her kit.