EDIT: This thread is not up-to-date for Starfall Prophecy. Some things have changed.
So, I've decided to put together a thread that addresses a lot of the more common questions about rogue class mechanics.
I'm also hoping that new players will post short questions here. And if anyone can think of a common question that I forgot to put on this list, feel free to let me know.
What type of weapons should I be using in my mainhand/offhand? Daggers? Swords? Axes?
It doesn't matter. Abilities scale off of normalized weapon damage, so the swing speed of a weapon doesn't affect anything. The only thing that matters is how much weapon DPS an item has.
(There's a single, very minor exception to this rule. If you're playing Nightblade in PvP, then using faster-swinging weapons will let you expend your stacks of Scourge of Darkness slightly faster, which increases your burst by a tiny amount. But the difference is so small that it's basically unnoticeable, so even then you don't really need to worry about it. And it doesn't matter in PvE, because you'll expend all of the stacks long before the cooldown is back up anyways.)
Does my offhand weapon affect anything, or is it just a stat stick?
It's just a stat stick for almost every soul. The exception is Bladedancer, which has two abilities that scale off of both mainhand and offhand damage: Binary Strike and Double Strike.
If you have two weapons with different amounts of Weapon DPS, put the stronger one in your mainhand.
What about my ranged weapon? Does that affect my melee damage? And do my melee weapons affect my ranged damage?
No, and no. (Aside from the passive stats on the item like Dexterity or Attack Power).
However, there are some melee souls that have ranged abilities that scale from melee weapon damage, like Nightblade's Twilight Force]. The rule of thumb is that if the ability is in a melee soul, it scales from melee weapon damage (usually mainhand damage, unless it's Bladedancer), and if it's in a ranged soul, it scales from ranged weapon damage.
For the sake of completeness, I'll note that Nightblade, Bladedancer, Assassin, and Riftstalker are considered to be melee souls, while all the rest are ranged.
Nightblade/Bard/Physician/etc have non-physical abilities. Does this mean that they scale with stats like Spell Power or Intelligence instead of Dexterity and Attack Power?
No. Every single rogue soul scales with "physical" stats: Dexterity/Attack Power/Physical Crit/Crit Power/Strength. (Yes, this means that Physical Crit affects non-physical attacks, and that Attack Power affects our healing abilities. The names of those stats are somewhat misleading.)
The spellcaster stats (Spell Power, Intelligence, Wisdom, and Spell Crit) do not affect any of your abilities in any way. You should never use any gear that has them.
What about trinkets, relics, and greater essences that say that they proc from physical attacks? Will my non-physical attacks proc those, or do they count as spells?
They count as physical attacks, and will proc anything that can proc from physical attacks. (With the exception of Tactician torrents, which cannot proc anything. See below for more information.)
Rogues do not have any abilities that are considered to be spells.
My Tactician torrents don't seem to be proccing trinkets or weapon enchants.
That's intended. Torrents cannot proc anything-- they would be super-overpowered if they could, since they hit multiple times every second.
However, crits from torrents can still trigger certain talents such as Increased Fire Power.
What is the rogue energy regeneration rate?
Rogues regenerate 20 energy per second.
I see a lot of different talents and effects that increase my damage and/or healing. How do these stack?
There are five basic stacking groups: passive, buff-based, debuff-based, mastery-based, and encounter-specific. Each group is additive within itself and multiplicative with the other groups.
Passive boosts are anything that is always active (IE not granted by some kind of buff, not even a 1-hour buff). Examples include Blade Finesse and the soul gifts.
Buff-based boosts are anything that applies a buff to you. Examples include Stalker Phase and Hack and Slash.
Debuff-based boosts are anything that applies a debuff to the enemy, such as Magnify Pain.
Any damage modifier from masteries is in its own category, regardless of whether it's passive, a buff, or a debuff. These are multiplicative with everything.
Encounter-based boosts are something that is specific to a given boss fight. For instance, the Goloch raid encounter has white circles on the ground that drastically increase the damage of anyone standing in them, while Primordius has a phase where he takes amplified damage. Despite being buffs or debuffs, these are multiplicative with everything (they are designed in this way so that they affect all specs equally).
These rules also apply to effects that directly affect damage taken-- in other words, mitigation talents.
Note that these stacking rules only apply to effects that offer direct, percentage-based adjustments to damage, healing, or mitigation. If something affects a stat (IE Attack Power or Armor), then it will be additive-- for instance, Burning Rage and Increased Fire Power stack additively even though one is passive and the other is buff-based, because they're boosting Attack Power rather than directly affecting your damage.
A quick comment on the implications of this-- because DPS builds tend to have extremely high passive damage bonuses, this means that further passive boosts from talents are generally less powerful than they appear, while the rarity of debuff-based damage boosts means that talents like Magnify Pain are more appealing, as your debuff-based damage multiplier is likely to be small or nonexistent.
How do the weapon enchant procs like Electrified Munitions and Virulent Poison work with AoE abilities?
If you use an ability that hits multiple targets, it can proc on each target, but the proc chance is divided by the number of targets that the ability hits. For instance, Electrified Munitions ordinarily has a 100% proc chance. But if you use an ability that hits two targets, it will have a 50% chance to proc on each target.
I've heard that Crit Power has a cap. What is it? And do any of the other stats have caps?
Crit Power has both a softcap and a hardcap. Past the softcap, you get less benefit per point of Crit Power. The softcap is 40%, and the hardcap is at 50% crit power.
Physical Crit technically has a softcap, but it's so high that it's not attainable (if you're curious, it's at 45% crit chance). If you were to reach it, physical crit would start to grant only 1/3 effectiveness per point past the softcap. And this only applies to the Physical Crit stat, not to talents that directly increase your crit chance. There's also a hardcap at 60% crit chance from Physical Crit, but it's a moot point anyways, because you'll never even get close to the softcap, let alone the hardcap.
Dodge has a hardcap at 40%, which you will never get anywhere near. Block has both a softcap and a hardcap, but I no longer know what they are with the heightened level cap of Nightmare Tide, although they both seem to be out of reach for now. Like Physical Crit, these caps only apply to the actual stat, not to raw gains from talents like Quick Reflexes.
Guard has a softcap at 2369 (which is 10% mitigation), past which each point has 80% reduced effectiveness. There is a hardcap at 4737 Guard (which is 12% mitigation). In T2 raids, the stat scales differently, and you instead need 3380 Guard to hit the softcap of 10% and 3910 rating to hit the hardcap of 12%. T3 raids have yet another formula, with the 10% softcap at 4500, and the 12% hardcap at 5700.
Dexterity, Strength, Attack Power, and Endurance are not capped in any way. Armor and Resistance have diminishing returns but are not capped.
Hit has a cap... sort of. For any given tier of content, there will be a hardcap for it, but the cap varies for each tier-- IE you need 800 Hit to be capped for expert dungeons, and 1000 Hit for T1 raids. Hit requirements for any given tier of content are listed on the stat's tooltip.