Re: Lighting Sorc
Warmth: 1
Frozen Armor: 1
Chilling Armor: 1 (people may disagree, but you will often be in close for Charged Bolt if that is something you enjoy using)
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Charged Bolt: 20
Static Field: 1
TK: 1
Nova: 1
Lightning: 20
Chain Lightning: 20
TP: 1
Thunder Storm: 1
Energy Shield: 1
Lightning Mastery: 20
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Total skill pts - 89 (with 12 skills from missions, means its good at level 78)
Dump the rest in whatever makes you happy. The emergence of synergies makes a ton of differences in Sorc builds now, so note that. I don't think that much of Nova (except for as a synergy) nor Thunderstorm, but ymmv. Warmth, TK, TP, and Ch.Armor are one point wonders. I do like Charged Bolt (unlike many here), mainly because it doesn't have the wild fluctuation of dmg that the others have, and with a good FCR, you can spam the hell out of it doing tremendous dmg to mobs, which is a sight to see.
For the build above, you keep up your defensive skills and then fight according to your enemy. For most mobs, a Chain Lightning followed by a spam of CB is sufficient. For tougher mobs, Chain Lightning and then Lightning.
Note that with an Infinity runeword equipped merc (NM Act 2, for Holy Freeze) will give a decent -LR that could probably break most immunes making you one tough cookie. Having max'd block couldn't hurt either, I get nervous about playing with CB since its most effective close up, where you're likely to get hit once in awhile.