This post is getting downvoted to hell, but idgaf because sometimes a counter point needs to be made against the most popular arguments.
People are arguing that fee 2/damage 3 doesn't work simply because its too oppressive. That spending coins efficiently and converting them into damage is simple too much to handle. However, I'd like to draw attention to the following points:
Not everything tunnel drill removes is conveniently a multiple of 3. If your prime removal targets are at 4,7, or 10 strength, drill is going to have to spend 2 coins for 1 damage at a certain point, or choose to let your engines stick for an extra turn. Neither is desirable.
If you play SY frequently, overprofit is a serious problem. Good spenders like Tunnel Drill help compensate for coins lost to overspending, or awkwardness caused by the avoidance thereof.
Most of the other good spenders (Jacques and Jackals) play into tall removal. Quite hard, actually.
Damage is the only way to guarantee that your coin value actually sticks and doesn't get removed by Yrden, Schirru or Heatwave or what have you. And why should coin value being denied be fundamentally a part of SY gameplay? Why do you think the faction has been in the dumper for like 6 months?
Tunnel Drill is massively telegraphed. Basically if your opponent has 8+ coins in the bank and some crownsplitter pockets set up, you know that they're planning either a Phillippa or Tunnel Drill. Seriously if they haven't played one yet, they're about to play the other.
Tunnel Drill is easily removed or mitigated. You can lock it, move it to the other row, or damage it by 5. It's pretty fragile.
We are currently in a removal/control meta. Most bronze engines just aren't meta right now. That's not Tunnel Drill's fault.
Drill gains only 1 point every time it spends. The other points are simply gained from your opponent having coins.
If I were to change tunnel drill, the most drastic changes I'd introduce would be:
Remove its profit (who cares anyway)
Make it melee locked (it pretty much already is lol)
Convert 1 str into 1 armor, like Whoreson's freakshow. (Keep its durability the same while lowering its point floor).
Imo whoreson's freakshow should convert 1 armor back into str and possibly gain insanity. Help non-cleaver SY out a bit please, CDPR!
One final word: I'd like to see bronze engines come back into the meta. I think that the best way to do this is to add more bronze engines that deploy at 5-6 points (including armor). I'd like to see bronze engines that trade up harder versus removal, probably at the cost of playing for less than 1 point per turn.
Thanks for reading! The downvote button is to the left and up a bit.