Well. I have experience with the bone spear necro, i made one this ladder season in fact. The first big hurdle is mana consumption. I only got to what i call sort of mid-range gear. Though that actually did okay in early hell mode, i was also a bit squishy. But the damage is good, and when you get past the mana issue, you can keep firing and damage a lot.
If you want to fork out the fg for a novelty build, i think it is worth considering the bone necro. You also get the break magic resist charm in d2r, so that's another motivator. But i do think they are relatively expensive, enigma is a must, and having superior gear to prevent deaths is also mandatory. I do not think 1000 fg is an underestimation. Of course depending on where in the ladder you want to make it, if you want to make it early, i gather d2r has even shorter ladder seasons - i can imagine you can quadruple that price too.
But necro is a popular build, bone spear is magic damage based, i'm not quite sure though in the terror zones if there are many magic immunes, like in the uber bosses, the minions are 5 x immune aren't they. But the magic damage on bone spear is relatively high, and like any resist, you need high damage to do good against high resist monsters. But i also gather there are -% enemy magic resist gear in d2r now. So that makes it even more worth considering.
I would definitely consider it.
But one big .. well, strong negative factor is the lower hit point on the necro. I mean as opposed to barb, you will probably have at least 2000 hit points less if making a super strong geared build. Probably in the range of 2500-3000 hit points, which is okay, but teleing randomly in high level areas in hell, well, heh ... that can quickly get eaten up.
I would wait for people with more experience before deciding to fork out the big coyn for this one. But i can sign that it is a relatively fun build, the spears pierce and hit 100% of the time, it's easy to hit things, i mean the pixels "catch" enemies even if like 0.8 yards away from them, sort of like the lightning fury. Only you know it will always pierce.
One thing more to consider is that you need to invest heavy in the bone skill tree, leaving little to nothing else for golems and others. If doing golem, probably clay is the option, a high level clay golem can slow the bosses and work to your advantage that way. But it does require at least some investing in it, 15 CG and 10 to golem mastery or so, before +skills, will probably bring it to a respectable hit point threshold. Maybe 2500 or so. And it's easy to spawn a new one when you get superior mana pool+regeneration. I mean it is probably the best choice to use spirit on the merc, you do the main damage with magic, so using merc only for utility is the thing to do.
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