First, I have found reference that the hit effect bonus scales with skill, but that leaves some room for guessing. Which effects are boosted? Hit area, hit lower defense, leeches, magical attacks? How much is the damage increase, and does it fall under the item / effect cap? How much are the hit effects boosted with skill? Is the hit effect boost affected by SSI on the weapon (like leeches are)? Second, I would like to point out that the ninjitsu guides on the site list minimum skill for focus attack as 60 vice 30.