I think there may be some misunderstanding with what the set bonus does.
When you Run Through, sometimes you get a buff on yourself that makes the next time you use Roll the Bones grant you one additional buff on top of whatever it already would have given you.
It does not give you a 25% chance per buff you did not get from Roll the Bones to get that buff.
If you choose Slice and Dice as a talent, you get a bonus to attack speed. The tooltip should change dynamically if you pick that talent.
With the 2 piece bonus:
Run Through procs a buff on yourself that gives you +1 bonus buff from your next Roll the Bones. You press Roll the Bones and happen to get 1 buff (base) +1 buff (set bonus) for a total of 2. Your set bonus buff has now gone away. If you press Roll the Bones again because you didn't get your favorite two buffs, those two buffs go away, and you may get 1 buff, or 2, or 5 on your next press. You have lost the 1 bonus buff from the 2-piece until Run Through procs for you again.
Maybe I misunderstood what is being discussed here.
Are you saying that for some reason when you get the set bonus to proc, and then use Roll the Bones, that for some reason you may want to immediately press Roll the Bones again if the buffs you gain aren't the ideal combinations?
Or are you saying that when the set bonus procs, you immediately want to use Roll the Bones as soon as you can? Is the concern that you potentially overwrite the set bonus buff or that the set bonus will fade before you Roll the Bones again?
Also it should work just fine with the Loaded Dice trait. If Loaded Dice and the set bonus are both lined up to happen, you should get 3 buffs guaranteed.