I know a lot of players are currently skeptical about MCH's dps performance, and I do not claim that this one idea will fix all of it's problems. But I think it would be a really good start to fixing it while still keeping the style of play that was intended.

My suggestion is to change Split Shot and have it like this:

Split Shot: 70 TP Delivers an attack of 140 potency to target.
50% chance to increase potency of next Slug Shot
70% chance to cause the next Split Shot to increase potency of next Slug Shot
Ammunition Effect: 100% chance to increase potency of next Slug Shot
100% chance to cause the next Split Shot to increase potency of next Slug Shot

Horrible personal writings of tooltips aside, I think this is an acceptable change to Split Shot. Essentially, it gives a chance for Split Shot to proc the next Split Shot to guarantee it's Enhanced Slug Shot proc. An "Enhanced Split Shot" if you will. What this does is have the MCH casting Split Shot less, and using it's better skills more, while still having rng play its part and sometimes forcing the usage of multiple Split Shots, only less than MCH's currently may have to spam it now.