The Lee Sin Q change makes him better vs champs, but worse vs objectives
When the bonus damage was 8% of missing target health that was better vs dragons and baron with their huge health pools.
You've shifted his strengths more towards assassinating champions and away from securing objectives. It's kind of a disappointing thing to see in the patch notes during a meta when champion burst is already too high.
This is the type of change that digs the hole deeper. This champ isn't competing as well as you'd like in the 1 shot meta, so you buff his ability to 1 shot instead of dealing with the underlying problem of 1 shots being too easy and common.