It most certainly is not worth it. Though I don't regret my Ninjutsu merits one bit, all my faith in my Ninjutsu Skill+ items (I had everything) died the day I saw a Warrior land Jubaku on Kirin.
Yeah I saw a lvl 1 mule hit Vrtra once with his lvl 0 dagger skill. I'm no longer capping my weapon skills or using A+ weapons. Nor will I wear accuracy or attack gear... since as long as someone else can do it once in a blue moon, its useless to actually be efficient in my debuffs.
HUGE difference between sticking 1/100 debuffs and a fluke then actually being able to efficiently debuff an HNM a higher majority of the time. Ask any RDM what happens when they try and spam debuffs on Tiamat if they wont stick. Ding! Dead RDM after 45mins.