I will give a comprehensive list of one point wonders and possible skill developments:
Bone Armor: Maxing this along with Bone Wall and Prison will yield you 800-1000 points of Bone Armor allowing you to wear Ethereal Items without breaking. (30k Defense Necromancer)
I've never heard anyone putting more than one point in this skill. I don't think even the people over at Hardcore would do this. I mean, sixty points for your Bone Armor? Perhaps a meleemancer would do this, now that I think of it, but otherwise I'd say it's wasteful.
Corpse Explosion: Maxing this will hit diminishing returns because this skill is not synergestic with your attacking power unlike Skeletons, Golems. I suggest anywhere from 1-10 points.
Like MYK pointed out, this skill actually gives increasing returns, because the radius is increased lineary, which makes the increase in area covered exponentially. However, later on you say that your army makes most of the kills. Which is not true; decent use of CE (even with only one point) will get you much more kills and more points in it will make it even better. However, I don't really know what you're trying to say about CE, because at one point, you say your main killing power comes from your minions and later on you say CE is abusable?
Amplify Damage. A friend accidentally maxed Amp Damage, giving him a huge curse radius very useful for summoner and Ubering. However, too many points is not advised. 1-3 points here.
For a Fishymancer, I'd say maxing it is really a good idea. Less AD cast means more CE cast which results in faster killing speed.
Decreptify: Although we know that Decreptify's radius is handicapped but additional points can increase duration (may be very useful in dueling). 1-3 points here.
Iron Maiden: Well some people max this. Will do significant damage in hell when stacking a maxed Iron Maiden with Level 20 Thorns and Heart of Wolverine from Bramble. Useful against Smiters because they hit 100% of the time; Time to take their damage back at them
Lower Resist: Although putting one point and maxing it will yield a difference about only 5% due to diminishing returns (-61/62% vs -66/67%), the only way to increase you elemental damage is to push for a higher lower resist. This may not be desirable Necromancers who use this skill, inclulding Poisonmancer, Elemental Battle and Lord of Magi before they are level 95. If you hit a very high level and you have nothing better to invest in this is a good skill. Still, it may not be the most effective since 5-10 points will give you additional 3% and 10 more points will only yield about 2%. So if you want a balance, 5-10 points here.
Maxing it, however, is certainly excellent. I'm talking about team play applications here. Two poisonmances can cover each other's backs, or a Poisonmancer and a LoM Nec. Excellent for baaling with sorceresses. Final note, some monsters are difficult to break since Lower Resist works at 1/5 effectiveness so you have to reach a certain number to break it and maxing it would give most insurance against all monster types
I don't know whether that was your point, but maxing it can indeed be a good idea for the increased radius.
Clay Golem. 1 point is great. 10 points means a very slowed enemy whether it be Player or Boss, 20 points is maximum slowness. Plus Clay Golem can boost the Attack Rating of your Iron and Fire Golems. Game code is: +Ar from Golem Mastery (+25/Slvl) and from itself (+20/Slvl). So it is 4/5ths as effective as Golem mastery, decent when comparing that to other Golem synergies (Blood Golem is only 1/4 as effective as Golem Mastery, and each point in Fire Golem gives relatively small amounts of damage. If you want to combine use of Clay Golem with other Golems, additional points in here is recommended. Either 1, 5, 10, 15, 20 points is good here.
Correct me if I'm wrong, but I thought slowing enemies in Hell was capped at 50% (for a single source), which is reached at skill level ten. I'd say, leave the skill level at one and let your +skills do the rest, unless you're making a Golemancer or something.
Fire Golem: I strongly recommend more than one point if you want to use your Golem for damage. Place points here when you have reached very high character levels and you do not want to invest in other points with diminishing returns (AHEM* thank you Blizz for putting diminishing returns on almost all Nec skills) like Corpse Explosion, Summon Resist, Lower Resist.
Fire Golem will increase the damage of your other Golems, Code is skill ed% = 6 * baseSlvl_FireGolem This is alot and will multiply the damages of your other Golems several times. Unfortunately, it only accounts for base damage so in the case of Iron Golem you'll only get a small damage increase.
Maxing Fire Golem will only give a 120% ED to other Golems. Golems do lousy damage and not even doubling it will give significant damage. If you want significant damage, make an Iron Golem from an item with Crushing Blow.
Prebuffing is advised when using a Fire Golem, and will become effective if you have a high level of Lower Resist or playing with another player with Lower Resist. A base Slvl 20 Fire Golem will yield ideally a level 45 Fire Golem, and a Slvl 20 Fire Golem will yield a level 35 Fire Golem, which marginally begins to do damage.
1 point will suffice here until you are undertaking a special build or you have reached a high enough level to complete most of your other skill tree developments. 20 points otherwise.
Revive: Well maxing this may be of marginal benefit if you like a specific monster class so much you want to carry as many monsters of that type around you as possible (e.g. Bunning Souls, Death Lords).
Summon Resist: Another spell that varies widely in skill distribution by personal preference. Skeletons Warriors and Magi after a +6 Battle Orders or higher from barbarians is pretty much invulnerable to anything besides elemental damage. For those who believe the best defense is the best offense and those who want to run a full army without ever having to resummon a skeleton, additional points here will help. Note that the diminishing returns here are much more generous than that of Lower Resist. 1-7 points here should be good.
Also, Summon Resist is the only way to deal with Sorceresses, and thus the ideal NecvSorc summoner would be a vita build with good investment on Summon Resist. It is the only way to decrease their massive damage and keep your minions for fractions of a second longer; enough to win the fight.
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