You cite some damage numbers, but the error you're making is that you assume are using skills data that relates to skill level 20. In advanced game, you SHOULD be looking at the numbers for skill level 35 or even 40 (depending on itemization...)
Which leads me to my next point, specifically, that FOR ALL D2 character builds, itemization is the only relevant consideration.
"Boner" necros are extremely powerful PvP characters. Since there is no *significant* resistance to "magic" damage there is little your opponents can do to mitigate the damage done by your bone spells. The dominant boner strategy is to stack FCR and +skills, wear an enigma, and if you're ranged elemental damage then some sort of resistance gear and they've got an EXTREMELY good chance of beating almost any other build (of any class) in PvP. They tele around, casting auto-targetting bone spirits and never let you get near enough to engage in melee.
Further, well geared poison necros are very viable for soloing the endgame. Sure, they are not the fastest killers, but they are extremely hardy. There are very few things that the game can throw at them that they won't be able to handle with relative ease.
In my opinion, the curse tree is one of the weakest, requiring AT MOST a single point in each skill.
It is easier to write an incorrect program than understand a correct one.