You're making an assumption. You're assuming the devs looked at it and said "It's hitting up to three times now. That's okay. Dark monks need the buff. We'll leave it in."
What's more likely is that the dev's looked at it and said "It's hitting up to three times now. That's more damage than we wanted it to do. It's not a huge deal. We can fix x, y, and z before we worry about it"
While your assertion that it can potentially do up to 1875 damage instead of the aforementioned 1500 is indeed correct, the AVERAGE damage that you will receive from each button push has been reduced. If it was not a reduction in damage, you would not see people complaining.