I think Taurus missed the boat when they designed the M94. It all has to do with the geometry of the trigger mechanism. Wolff doesn't sell a spring kit specifically for the M94 because the trigger is so finicky. I have tried several different tricks to no avail to get the DA back with the Wolff spring.
There may be a spring that will be in between a Wolff and the stock spring that will give reliable DA. I haven't found it yet.
There is a 1/4" difference in the hammer travel of SA vs DA. So in order to get DA they had to put in the heavy spring to compensate for the shorter hammer travel.
I generally use SA anyhow with the lighter Wolff trigger spring and lighter hammer spring. I do enjoy shooting the gun with this set up.