So I got an AST friend to give me Spear, gave me a 16s recast for Ninjutsu instead of the 20s.
Pretty sweet.
So what's the bug with it? Does it not work sometimes?

Otherwise, Balance, Arrow and Spear are great for Ninja.
Spear is great because we have so many CDs and it helps Ninjutsu too. I would think NIN or DRG gains more from this than MNK.
Arrow can be great unless your mudra lag starts eating into the off-gcd, and we have a lot of other oGCD too. I think MNK and DRG benefit more from this than NIN.
Balance is great across the board for everyone.

Spire is great for melee AoE.