Like many Sorceress builds, the CL Sorceress relies heavily on synergies to make her spells do damage. Although Chain Lightning may not be the most damaging of spells (compared to other synergizing spells such as Blizzard or Meteor), and the inconsistency of its damage can be frustrating, Chain Lightning has the advantage of a significantly lower Mana cost, as well as the speed with which the spell does its damage.
The CL Sorceress will obviously max out Chain Lightning. However, she has a choice of three other synergies: Charged Bolt, Lightning, and Nova, all of which give +4% more damage to Chain Lightning. There is also Lightning Mastery, which when maxed, will give an amazing 278% bonus to all Lightning Spells. Depending on which of these skills a CL Sorceress decides to max, she can do one of two things:
- Max out Charged Bolt, Lightning, Nova, Chain Lightning, and Lightning Mastery. Rely only on very high-damaging Lightning Spells, with Chain Lightning and Lightning as the main offensive attacks. Is incredibly powerful, but completely useless against enemies immune to lightning (as many are in Hell mode).
- Max out only three or four of the spells (e.g. Lightning, Chain Lightning, and Lightning Mastery), then max another spell of a different element that requires little synergy (e.g. Frozen Orb or Fire Wall).
As a lightning sorceress, your mercenary will likely be your best friend- if you set him up right. The primary reason lightning sorceresses are so powerful is because they can do ungodly amounts of damage in less than a second (a good bolt of Lightning can do higher than 50,000 per shot with the right gear and build) and that they can have virtually no monsters resistant to them. Your key here is an Infinity runeword Polearm class weapon equipped to your mercenary. Infinity automatically runs Conviction (a Paladin aura that drops resistances significantly- nearly always breaking immunity past level 10), so your mercenary will make all your enemies (or at least most, some Super Unique monster might still be immune) as defenseless as a Normal level Carver in Act I. With an Infinity, as long as you do a few thousand damage per hit of Lightning or Chain Lightning, you'll be able to kill just about anything, even in Hell mode.
If you can't afford more skill-boosting gear (like Lightning Skill Grand Charms (Sparking prefix), try to get items with FCR (Faster Cast Rate), so that you increase your amount of shots over time, effectively increasing your net damage.