Mobility and Damage should be on a scale.
If you have a ton of mobility you should have substantially less damage than an immobile counterpart. Since mobility (and I disagree with this) is a skill expression mechanic then the rest of the kit should be lack luster as to be made up for.

etc. Should have overall low damage that has a consistent value overtime, with 0 steroids or burst mechanics. The only one that comes close is Gnar and to an extent jax. Even as assassins, the mobile ones should do less damage than the largely immobile ones.
Cha, call me old school.