Character stats are the lifeblood of tweakers, tinkerers and twinkers in any MMO. The basic formula is always "higher stats = more win," and this is as true in Star Wars: The Old Republic as it is anywhere else. But it's senseless to stack up on stats you don't use, or to build some of them up past the point of usefulness.
SWTOR has 6 basic stats of the RPG-standard variety. Four of them are primary stats for the different classes, and two of them are auxilliary.
Strength - Affects melee damage. Primary stat for Jedi Knight and Sith Warrior.
Willpower - Affects Force abilities. Primary stat for Jedi Consular and Sith Inquisitor.
Aim - Affects ranged damage. Primary stat for Bounty Hunters and Troopers.
Cunning - Affects tech damage. Primary stat for Imperial Agents and Smugglers.
Endurance - Affects total health and health regeneration. Secondary stat for all classes, important for tanks.
Presence - Affects companion effectiveness (health, damage).
In general, players will want to increase their primary stat first and Endurance second. Tanks are a special case - they will want to have very high Endurance, and their Primary stat may take a back seat. All other stats provide only trivial combat bonuses and there is really no need to increase them beyond their base scores.
Some players may be confused by the descriptions offered in the tooltips, and may want to build up non-primary stats in the mistaken belief that they will be improving their characters. For example, Bounty Hunters might be tempted to use Cunning mods to improve their tech-based attacks (flamethrowers, missiles and anything else that doesn't come directly out of a blaster), or Jedi Shadows may believe that stacking Strength will make their lightsaber attacks more powerful. This is incorrect - each class has a primary stat that affects all their skills, and receive only minor boosts from the lesser stats. For example, Jedi Consulars use Willpower to determine their lightsaber damage, and Sith Juggernauts use Strength to determine the damage from their Force-based attacks.
As a character levels up, he gains automatic stat points per level. His primary stat increases by 4, Endurance and Presence increase by 3.5, and the rest increase by 0.9. For calculating damage, each point in the character's primary stat is equal to 0.1 damage (10 stat points = 1 damage point). For Endurance, each point is equal to 10 health points and 0.2% health regeneration.
While the basic stats have a blanket effect on all combat abilities, there are an assortment of advanced stats that have more focused effects on specific things. These are the fine points of the build, and this is where the real math of character tweaking comes into play.
Most of these advanced stats are subject to diminishing returns - the higher the number of points, the less benefit the character receives per point. As an example, a player has 100 points in Surge, which equates* to a 0.5% bonus to his critical multiplier per point in Surge, for a total of 50%. If he stacks Surge and builds it to 200, according to the diminishing returns curve, he will only get 0.3% per point - a total of 60%, only 10% higher with twice the Surge rating. If he continues stacking and builds it up to 300, he will only be getting 0.21% per point - the total would be 63%, a very minor increase considering the effort it takes to build the stat that high.
* - These values are not technically accurate, and are only used for the purpose of illustration.
When considering stacking a stat that has diminishing returns, the player will want to aim for the optimal range in the curve - the "sweet spot" where they are getting both a decent per-point increase and a high rating. Stacking beyond the sweet spot is essentially wasting points - the lower per-point gain means that it will be more effective to start building up another stat. For example, when a healer reaches the sweet spot in Critical, he will want to start getting gear that adds Surge instead of continuing to stack Critical, as Surge will offer more results for the investment than more Critical would.
In general, the cutoff is around 250 - 300 points for advanced stats with diminishing returns. Anything beyond that provides too little benefit for too high cost, and those new points can be added to something else instead.
Power - Generally, this stat has a blanket effect on all outgoing damage and healing. This is the only stat that is not subject to diminishing returns, and is highly desirable for healers and DPSers.
Force Power - This stat functions the same as Power, but only affects healing and damage done by Force skills, and is useful only to Jedi and Sith. Not commonly found on mods.
Tech Power - This stat functions the same as Power, but only affects healing and damage done by Tech skills, and is useful to Troopers, Smugglers, Imperial Agents and Bounty Hunters. Not commonly found on mods.
Accuracy - This stat increases the likelihood that your attacks will hit. Basic attacks (the zero-power attacks you start with at level 1) have a base 90% chance to hit an on-level target, and "special" attacks (which are everything else) have a 100% chance to hit. Increasing accuracy over 100% means the opponent is less able to defend against it using Dodge or Deflect. This stat is useful for dual-wielders, as the accuracy of offhand attacks is lower than the accuracy of main-hand attacks.
Critical Rating - This stat affects how often attacks will hit for critical damage, and how often heals will cure critical amounts of health. This is particularly desirable for DPS and healers - being able to land crits frequently makes these characters much more effective. This stat is subject to diminishing returns.
Surge - This affects the magnitude of critical hits and heals. The base multiplier for critical hits and heals is 50% (that is, criticals hit for 50% more damage than normal hits), and Surge Rating adds a percent bonus to this multiplier. This stat is subject to diminishing returns.
Alacrity - This stat affects how quickly skills are executed. Any skill that is channeled or that has an induction is affected by Alacrity. This is somewhat desirable by healers, especially in PvP, as it will allow the long inductions and channeling of healing skills to finish faster. It's also somewhat useful for DPS-spec Sith Sorcerers and Jedi Sages for the same reasons. Be warned that high Alacrity can lead to burning through the character's power pool very quickly, and that the stat is subject to diminishing returns.
Defense - This stat affects the character's ability to Dodge or Deflect ranged attacks, and is desired for tanks.
Shield Rating - This stat affects the likelihood that a character using a shield generator will activate his shield to absorb a portion of incoming damage. The base chance to activate a shield is 5% (inherent with all offhand shield generators). Characters who do not use shields have no use for this stat.
Absorption - This stat affects how much damage a shield will absorb when activated. This only takes effect when the character's shield is activated, as dictated by Shield Chance. Base absorption is 20% (inherent with all offhand shield generators), and Absorption rating adds a bonus to this. Absorption is useless to characters who do not use shields.
Expertise - This stat affects damage output, damage reduction and healing output in PvP only. At lower levels, stacking Expertise gives players a distinct advantage in warzones. In level 50 PvP, it becomes mandatory for survival.
For quick reference, here's a handy chart to help you determine what advanced stats you will likely want for your character.
|Class/Spec||Power||Force Power||Tech Power||Accuracy||Alacrity||Critical||Surge||Defense||Shield Rating||Absorption|