Is Alex Prime a good example to really be using? War didn't have Fell Cleave spam until SB, we basically doubled our amount of Fell Cleaves since Alexander, no? Actually at just a quick glance it looks like we've nearly tripled FC spam since HW. Alex prime around 20+ FCs, NeoExdeath around 40+ FCs, and God Kefka I'm seeing logs with around 60 FCs (prolly thanks to 90 sec spam intervals vs old 120 sec IR)

At any rate, it stands to reason crit FCs would've been a much larger chunk of DPS during Deltascape when it was being made a big deal because you had double the amount of them. You won't see it now since the majority of them are automatic DHC.