The penalties from Seigan + Hasso are far too great to make solid use out of Utsusemi. If you need that extra wall of defense, I guess you could go sam/nin with a FC set. You'd be much better off cancelling Seigan/Hasso if you're subbing NIN and using it as needed, as the penalty is harsh. At that point, would be better to change main jobs because NIN sub and SAM main do not mix well at all.
This.....
There are 12345678 DD in game with better synergy with shadows than a job that rely on hasso for ja haste. THF is pretty damn strong as 1h DD and like all other 1h it has good synergy with shadows. DRK and DRG has ja haste without having to rely on hasso. I haven't check spreadsheet but theres a possibility that war fencer savage build also beat 2h without ja haste up.
That being said, it is possible to clear entire wave 3 and boss without shadows at all, just use wilt, and turtle a bit more on war mob(I think volte cleaver is their name), then you can probably live through it. Our 2h never sub NIN for wave 3, although on cor I personally feel a lot more safe with shadows so they do help, just not essential for wins.
On megaboss /drg may save you more than shadows because capped hate is usually what kills people. Some report bosses randomly use deadly aoes, but they seem to be random as hell since there are also groups never see deadly aoe move entire run.
Cerberus.Shadowmeld said:
»20% FC on precast is about all that is needed to get shadows up in between hits.
This may be the case for ni, probably not the case for ichi. Unless you have capped spell interruption set I do think getting close to 80% is important for ichi. Since ichi overwrites ichi but not ni I tend to priorize ichi and just spam them for situations that I need to tank thinks then use ni as backup. I can usually keep shadows up forever that way unless the mob has adds or wipes shadows.
Cant count how many times having capped fc for ichi saved my ***.