Thrown Hatchets are weak because they don’t synergise well with most attribute perks. Currently the 100 Strength Perk is:
+5% damage to melee slashing and strike damage
A very simple way to buff Throwing Hatchet would be to remove the “melee” requirement.
+5% damage to slashing and strike damage
This change would not impact any other weapon aside from the Thrown Hatchet, as there is no other ranged slash or strike damage in the game.
Alternatively, Thrown hatchet could be made to deal Thrust damage in order to have better synergy with Dexterity perks. That is all.