Needle spam has been way too strong, especially since the buff.
Spamming it makes faithless Shaitan priests do nearly as much dpt as Lich Evokers, while also healing a decent amount.. and that's before you count characters with actual RES.
I suggest raising it to 4M.
I agree with the proposed change. Currently the spell is very similar to how Nitrogen Drop was before: spamming it wins battles.
Personally, I quite like it's utility as a spell that does damage independant of stats for the sake of RNG-gimped characters, enabling them to actually struggle on to 60 for their first LE. However, the fact does remain that 180 unresistable (Outside of Elemental Resists, Etc) damage per turn is pretty intense, and completely invalidates the point of making a more Res-based character sice you'll just get needled anyways.
While raising it to 4M seems reasonable enough, I'd also suggest the proposal of limiting the damage to 12 per needle instead of 18, while changing the detonation healing effect from half to full, and removing the detonation damage. That way, if you desperately need the needles' damage, you can squeeze a little bit more out of them (than one use currently gives) with a second use, while buffing the secondary supportive effect to retain it's usefulness as a utility move. Weaker than dedicated damage/ healing, but filling a middle niche. (60 damage + 60 heal when detonated with another spell, vs 90 + 45 heal/damage when detonated, and 120 vs 180 when doubled up on)
I think increasing the Momentum cost is a good way to balance it out without compromising its current power and function, so we'll try that.