A simple, clean Tunnel Drill change that would fix most of the problems with the card

Profit 1.

Tribute 2: Increase damage by 1 for each adjacent Crownsplitter.

Fee 2 (Melee): Damage an enemy unit by 1.

So there's two things going on here: the addition of Tribute 2 if you want to increase the base damage of the fee, and locking Drill to the Melee row.

The Tribute is the perfect way to decrease the total cap of damage this card can do and lower its damage on average. It doesn't completely deny you if you need to use the fee without Crownsplitters and it doesn't limit the reward of the ceiling if you manage to get the huge setup going (Bounty, Witchfinder, Crownsplitters, etc.)

Locking it to the Melee row is to allow opponents to interact with the setup. What if a deck like White Frost could move the Crownsplitters to the Ranged row prior to Drill coming down? Now you have interaction and the ability to deny a 25 or 30 point play before it happens.

Lastly, this is a Drill, not a trebuchet or catapult. It doesn't make sense to work on the Ranged row. Just some food for thought.