As you can see, there was merely 5 games played the entire week in the Challenger tier with Lissandra in it. That means there was 4 wins and 1 loss. That is an incredibly small sample, meaning that the win percentage has no real weight to it. Normally in statistics, the bare minimum for sample size is 30. To give some reference, the 5 most played champions in Challenger were in about 300 games each for the week. Their win rates still vary quite a bit, but they are much closer to 50% (seen below):