As said elsewhere here, doesn’t matter if it’s four or two or one. If you aren’t getting any to drop naturally, you aren’t getting those sparks outside of the method we’ve been using the last two seasons. You also need to remember they just give the solo players a huge middle finger by removing the regular uber bosses, leaving only the tormented bosses to get mythics from, denying soloers a potential, if somewhat more time consuming, path to a mythic as a drop.
Also, the two spark crafting nets you a random mythic, i.e. one that might not even be useful to you or that you already have.