SE HAS said that SAM was normally meant to be a tank job...and with AF Hands (?) and Roshi Jinpachi, some rice can give em +80def.. (hell, Tonosama will give +100att, +60def, +3dex, +3vit, +3chr, +2% double attack. HQ will give +120att, 80def, 4dex, 4vit, 4chr, 10% double attack) - Only get half the att/def/doubleattack by using only one, and even then it's still an amazing stat boost. Genbu's Kabuto could be a decent alternative too, as WSM said.
And as already said, SAM/NIN can be insanely cheap in the right situations (same parry as NIN plus Third Eye). /NIN doesn't hafto = dual wielding, either.