Yes, that is another shortcoming of offensive finishers: Whatever debuff they cause is almost certainly less powerful than Stunning Fist.
Note that when I pointed this out the day after monks were released, Eladrin responded by boosting the DCs of finishers, which had originally been identical to that of Stunning Fist. However, that change only helps against mobs who actually have saves good enough that Stunning Fist doesn't work well, which cuts out a big chunk of potential targets.