Some NW mechanics questions

Edit: In fact, most F/P mages cap their poisons at level 28, which is 95% HP poison (which is still enough to 1HKO after poison usually; DTs will be left with 1600 HP, Squids would have 2300 HP, Rissel Squids would have 2450 HP, etc, so most of these you could finish with one L7 or maybe one or two vamps).
I maxed it, because I like continuous poison instead of focusing on killing off with different skills

Oh, I definitely recommend maxing it over 28, I'm just saying that 28/29 Poison isn't much less efficient than max.

Really, anything over 28 is fine, but there's really no point in not maxing Sling since the two extra points would go to something useless like Sudden Attack.