This guide is written and researched by Discord user Ryamos, edited and published by Lucy at Expanse. Full credit goes to Ryamos, with his excellent writing and knowledge on DPS and class skills
I decided after helping various players over the years to write a KISS (Keep It Simple Students) guide to the three class types found in SWTOR. This guide is for the majority of players, the DPS players, who want to know what the quick and dirty end-game operations numbers are that they can be working towards from the start of their characters. Here you will find two breakdowns: the crit build, and the alacrity build and why each one is perfectly viable. Please note that these builds are dependent on play style and (in my personal opinion) your character's advanced class build.
This is the one number that is (within reason) non-negotiable for every single dps (and only dps) build: 110% accuracy rating. Every PVE flashpoint and operations boss has a 10% reduction to damage (of all the kinds), and our 110% accuracy rating cuts back that damage reduction. This is especially important in Veteran and Master operations where the enrage timer is reduced to around 5 or fewer minutes on bosses. Getting as close to this number (don't be surprised if you reach 110.56% or such) is the most important thing you can do to ensure you do your share of damage in the whole game. I personally start working to this number as soon as I can, though that's not a necessary goal for starting characters.
The second most important stat to work on, and the one that all your character's base damage will be derived from, is Mastery. There's no target number here, it's all about getting gear that'll increase your mastery stat instead: aim for enhancements and mods that have mastery highest and your next stat (crit, alacrity, power, etc) second highest. Endurance is a low priority as dps builds. Your armorings, barrels/hilts, and augments should all be Versatile ones; resistance is for tanks. You also absolutely have to have the Focused Retribution line of relics as they grant an increase in mastery when triggered.
Here's where you get into what makes your toon unique to you and what your play-style is: crit, power, and alacrity. Now, some of you may overlap these, some of you may play to one style only, that's up to you. The first build is your critical build, also known as “burst”. Critical information is broken down into two pieces: critical chance and critical severity. Chance is the likely hood of a critical hit happening with each attack. Severity is the percent increase that will be added to the attack's damage amount. The higher the numbers, the more often and more damaging your critical attacks will be. This can be particularly useful in character builds that have a lot of passives and actives that increase critical damage and chance for attacks, such as the Scoundrel's Scrapper build. Make sure you use the Devastating Vengeance relic for its critical boost.
The second build is your power build. This build will probably have an overlap of both crit and alacrity, and is good for players that want to deal some good burst damage but manage cooldowns quickly as well. Power will also add bonus damage to your attacks. Find a blend of pieces that increase mastery and power in your mods. Also make sure you use the Serendipitous Assault line of relics for the power buff it grants when it triggers.
The Third build is your alacrity build. This is the speedster build. This build is very good at managing cooldowns and regaining resources (ammo/force). The goal here is to ignore critical increases and focus on alacrity gains so that you're popping off fast attacks and regaining ability uses quickly. My favourite use of this is as a Combat Sentinel because our Zen increases our alacrity by roughly 30% and lets us really lay into abilities in rapid succession. I would recommend the Serendipitous Assault line of relics here as a crit buff won't be worth anything to you.