Ah poor Azami, we hate her for her use and love her as fodder. Is there a worse purpose for a unit?
Truthfully though I agree with lolix. Not many of us will have the best unit in the game for that class and we will happily take what we can get. Fran is to Vampire Hunters what Leanne is to Heavy Armors. Are they top tier, op units? Of course not, to think so would be foolish, but are they the best units we can easily obtain? In that case yes. Leanne will carry you for most maps at max skill level and Fran will do the same.
If you want to talk over-all performance that is a different story but even then, looking fairly at Fran's stats and skill, she is still a good unit.