The difference between Dancing Edge and Disembowl is:
WAR buffs a NIN's DPS as the only tank with the slashing debuff so using NIN to replace WAR isn't viable.
and
NIN's TP values are balanced assuming you use Dancing Edge.
NIN has always had this problem. It probably would help with both DPS and tank balance if they just reduced Aeolian Edge's potency by 30-40 and adjusted the TP cost to be ~55 for both, but you still have the issue where NIN loses one of their timers to watch in their rotation.