Wizkids Rules!

Mr. Fixit "Joe" - When Mr. Fixit KOs an opposing character die with combat damage, target opponent draws 1 less die during their next Clear and Draw step.

If I have two of these dice out and they both attack and KO opposing dice, does my opponent then draw 2 less dice during their next turn?

Yes. Mr. Fixit’s ability applies to each of its engaged character dice that KOs an opposing character die with combat damage. The following rule is applicable in this situation:

Rule 3.4.3.2 An applied ability will trigger “when” it occurs (e.g. "when fielded", "when attacks", "when blocks", etc.). These abilities happen for each die that is fielded/attacks/blocks, take place immediately, and last until the end of the turn.