Very nice take on the theme. I also had the same idea at first (Mine was a spear) nut I ended up going for a different idea later.
The mechanic definitely has promise but there are a couple of problems I want to point out:
1. The dart can get stuck offscreen. Most of the time you'll be rolling a dice hoping to hit something offscreen. When you aim, you should move the camera a bit towrds the aim direction.
2. Losing the dart when hit was a good idea at first but more often then not it'll get stuck in spikes. A way to recall the dart would be nice. Maybe even add a leviathan axe style boomerang effect where it damages enemies before returning.
3. Aiming should be done with a mouse. Also, draw a line to show where you're aiming and where you might hit. This can easily be done with a line renderer.
3. There are no visible health point but you die in 3 hits.
4. The dagger is hard to locate on screen since it shares the same color as some of the elements in the level.
Obligatory link to my game: https://b-deshidev.itch.io/nekurotactics