I agree with Wintersteel. The real value of a Fairie Ninja is getting in there close. The Cane incapacitates or insta-kills that often (it's happened to me even with Nessie a couple of times), that other tanks then make short work of the rest of the battle.
Additonally, with the stealth, race and and speed bonuses my FN's AC was in the low 20s from memory. Add to that a Fey ring (AC+5 with the stealth bonus), and FN's are almost untouchable. Their initiative is also the highest, meaning that they're almost always striking first.
For all these reasons, IMO up close and personal is best.
Proof is in the pudding, I've just started a solo game with a Faerie. He started as a mage w/77 int, lv-up to bishop and went for 5 or six lv-ups adding str and vit to get the stats to make ninja. I just completed stealth training last night in the upstairs area just inside the upper monastery against the three seekers.My strategy is to do the spell-less bishop thing with a few modifications. I plan to go back to bishop next but want to skip the rest of the monastery and go straight to Arnika for some PP training while he's still a ninja. After lv-up to bishop do the psionic and alchemy training, head up to Umpani Camp and then to mountain wilderness to the waterfall and get the Staff of Doom.
I'll play it by ear from there but the object is to go back to ninja for one level before I PP the Don for the Cane of Corpus. Maybe I'll wait until the bishop training is through, who knows. Part of the reason I love this game is it's flex-ability.
Any ideas will be given due consideration.