Spell details for Katon: San  

Not knocking on your choice of merits, just wondering why you'd go for one San spell rather than the whole wheel? Unless you put points elsewhere such as Ninja Tool Expertise or Sange.

Anyway, this spell is pretty nice, for Ninjutsu. With my 'normal' equipment on WAR sub it can do around 130 or so, I might have had some resistance there. on an xp mob (VT) With my INT gear (+33? Maybe more, my INT was a little over 100 total), 37 BLM sub, Vulcan's Staff, Melon Pie, Moldavyte Earring, and Ninjutsu Skill +20 (Ninjutsu Earring, Ninjutsu Torque, and Koga Kyahan) I got normally around 280, my highest capping at 293. This is VERY good damage considering it has a 3 second cast time, and no MP cost (and no tool cost about 15% of the time because of my AF2 gloves ^^; ), and NIN can actually deal with the hate unlike mage classes Nuking (Though evasion and Haste suffers because you're replacing that gear with INT/Ninjutsu skill gear). And of course it lowers resistance to the next element in the Wheel (or for other elemental magic users in the pt). This setup also has the added bonus of boosting Ni spells, up to 190 Damage for me(and rarely resisted except for the element the mob is strong against).

Once I get the whole wheel of San spells, that's ~1800 damage unresisted in about 30 sec (there's a small delay while animation is going before you can begin casting your next spell, and of course delays for recasting Utsusemi). And over 1100 damage in about 15 sec for Ni spells. Total that's a good 3k damage in under a minute, and with Haste you can cut your recasts to 45 sec or so for San spells. maybe not up to what a BLM can do in the same time frame, but a BLM can't survive doing 3k every 45 seconds :P

I'm still missing a bit of INT gear too; I can get an additional 10 or so INT by getting the +1 versions of a few things and a more expensive belt. Still not sure wiether AF mask, AFv2 Mask, or the INT from Yasha Jinpachi would be the best though. I'll expement more.

The only bad thing about all this is, it's a very expensive alternative when katana damage can do about the same with good gear. Good for Manaburst PT's maybe, or physically resistant things. I'd say good for Gods and HNM and such, but only to a point since they also just added in the resistance increase for repeated use for NM's :\ But still, a fun, if expensive, alternative to the standard NIN, once you hit 75. Since my NIN is pretty much maxed except for a Speed Belt and a Sniper's +1 (or Flame Ring; haven't decided yet, but I think I like the accuraccy more since I gave up alot of my acc gear for haste gear). Gives me an excuse to merit, anyways :P