adding on to what LONGSTON was saying the target time is actually dependent on the highest strength or magic stat of your party so just stacking one character will actually make it harder. I just used level one weapons of the lowest teir and didn't use any strength or magic accessories. This lets you use things like imperial armlets and other damage reducing items allowing you to to stay in paradigms without a medic. The extra time with 3 non-medic classes will make up for the loss in stats but you will still have more time.
P.S. The lionheart is a nice small bonus to use as your lower weapon on lightning since the early stagger could possibly shave off those last few seconds that you need