Usually when I make a suggestion like this, people will complain "You don't play ___ mastery, so you don't know why it's difficult!" So I got bone mastery. It is not difficult. It's basically a slightly worse custom moveset.
First of all: It's stupidly easy to land. The E, in both cases, has an absurd hitbox, infinite piercing, and the mastery is just a homing missile version, which can loop around. Once again, this is the problem: No damage should be completely unavoidable. GP's nuke can be escaped. Midas's hammer can be dodged. But Bone has an insanely difficult to dodge E and guaranteed Q. It's like old Time, where it just froze the whole map.
Second: It has insane damage for a low-punch ability. 25% of your health. That's how much damage the Q deals if you get caught on the edge and immediately leave. You can easily kill a Midas with this just running and E and Q spamming. The combos with Q are also immensely high-damage. For example: Q + basic 2-hit combo can deal 50% of someone's health. And getting 3 blue bones with mastery Q, while not every use, still appears fairly often. This, combined with mastery E, can instakill or void with the ridiculous knockback or deal 75-90% of your health.
Third: It doesn't encourage fighting or building melee skill. Basically the entire ability is centered around voiding/running. Someone chasing you? Use Q to blockade them, or E to push them all the way back. There's no melee element except for punching a person trapped in Q who can't move. Plus, people might not even know that blue means "don't move".
Balance Changes: Prevent Bone users from entering their Q, and slightly nerf the hitbox of E. Q is the main problem for its damage, and it would be much more on the point of the ability, due to it being entirely based off of "Don't move, and you won't take damage." The hitbox for E is too large for something that does more damage and as much knockback as Malice E, and just making it avoidable would be great for balance.