1aim at the floor, not the enemy
The head pierces everything in its path on the way out, but the real damage happens when it slams into solid ground. That impact throws out a wide blast that reaches through walls, so lobbing it into the dirt or ceiling next to a group hits far harder than a clean line drive that sails past them into open air. Get used to throwing at surfaces.
the blast only happens outbound
On the way back the head passes through terrain and detonates nothing, so you get one blast per throw at most. It also has to be in flight for a moment before it arms, meaning a throw at a wall you are standing against gives you nothing. Open rooms with a floor and a ceiling in reach are where this weapon lives; a wide sky arena is the worst place for it.
confusion is real crowd control
Both the head and the blast can leave enemies confused, which turns ground walkers around and sends them away from you. Against a corridor full of things closing in, that is often worth more than the damage.
when you will find it
It comes out of the wooden fishing crates, which you can open long before hardmode. Nothing stops you from stockpiling one early and having it waiting the moment the Wall of Flesh goes down.