Solo'd this lil cactus today with my 57blu/28nin.
Incredibly easy to kill provided you have some form of shadows and or stoneskin or 1020+hp ...
1000 needles will eat up shadows and will take stoneskin down quick but will absorb some f the damge so it is pretty useful imho.
I kept utsesumi up as well as metallic body and when i got the sabotender around 25% hp left he used 1000 needles. With both utsesumi and metallic body up he did only 548damage and i quickly dispatched him with a few spells after that..
I later had 1 jump me while engaged (pop), and both used 1000 needles ..I died but killed one of them. Learned spell so all was good..