SW:ToR Tanking and the Assassin

What We Know About Threat
1) All damage has a threat rating of 1.
2) All healing has a threat rating of 0.5.
3) All abilities listed as "does additional threat" have a threat increase of 0.5.
4) Tank stances increase all threat ratings by 0.5.
5) In order for aggro to change targets from melee range, the aggressors threat pool has to be trumped by a rating of 1.1.
6) In order for aggro to change targets from range, the aggressors threat pool has to be trumped by a rating of 1.3.

What we don't know is how some of these factors work together.
- An example of this is the interaction between 3 and 4 and whether or not the modification is additive, multiplicative before stance modification or multiplicative after stance modification.
- Another thing to consider is the interaction between 5 and 6. According to Gankstah, these numbers result in a very realistic scenario where threat is harder to lose but also harder to reaqcuire. What does this mean for the dps/tank interaction? Tanks will have to work their ass off to reestablish lost aggro and a dps will have to completely dump their rotation for several cooldowns so that they won't threaten to pull aggro again.
- Another unknown is the way that healing threat is distributed and whether or not TOR follows other established MMOs in using a even distribution model. For example (as seen in WoW and Rift), if you healed for 2000 and have 5 targets then 1000 threat (remember healing threat is 50% of the value of the heal) would be split 5 ways among your targets for 200 threat per target.
- Finally, we have no idea if taunts actually have a threat component or not. My guess from experience is that they don't, and merely force your opponent to attack you for 6 seconds.

Baseline DR/Shield/Avoidance Calculations
WARNING: Heavy mathematical calculations ahead! These calculations are copied directly from Gankstah's primer where he mentions the following caveats:
1) Everything is listed for Imperial classes which are direct mirrors of their Republic counterparts - you will have to look up your own talent names to plug in if it really bothers you.
2) Everything here is always subject to change at Bioware's whim.
3) This information is for comparative purposes only as these calculations are only part of what corresponds to any given tanking class.
4) The provided calculations assume level 50 premium armor values. The BAV (base armor value) is representative of a full suit of each armor class.

Modified Armor Value (MAV)
- SI: (BAV Light 1909)*(Stance 2.5) or 1909*2.5 = 4772.5*(Eye of the Storm 20%) or 1.2*4772.5 = 5727
- SW: (BAV Heavy 3601)*(Stance 1.6) or 3601*1.6 = 5761.6
- BH: (BAV Heavy 3601)*(Stance 1.6) or 3601*1.6 = 5761.6*(Rebraced Armor +16%) or 5761.6*1.16 = 6683.5
Note: Armor bonuses are multiplicative exceptions to TOR's mountains of additive calcs. Now, we plug our MAV into our DR calculation (found in the Game Calculations section) to come up with our Base Armor DR (BADR):
Base Armor DR (BADR): SI = 34.65% | SW = 34.78% | BH = 38.22%

Modified Base Armor DR
TOR handles passive skill bonuses additively and NOT multiplicatively so let's plug in current DR passive skills:
- SI: (BADR 34.65%) + (Sith Defiance 2%) = 36.65%
- SW: (BADR 34.78%) + (Stance 6%) = 40.78%
- BH: (BADR 38.22%) + (Stance 5%) + (Ion Shield 2%) + (Power Armor 2%) = 47.22%

Resistance: Elemental/Internal DR
As mentioned earlier, Elemental/Internal DR does NOT factor in Armor. So after subtracting Armor and adding passive Elemental/Internal bonuses we get the following:
- SI: (Sith Defiance 2%) + (Charge Mastery 9%) = 11%
- SW: (Stance 6%) + (Dark Blood 4%) = 10%
- BH: (Stance 5%) + (Ion Shield 2%) + (Power Armor 2%) = 9%

Situational Modifiers
These are situational modifiers from abilities that directly affect DR. I mention these separately because the effects are longer than the CD so they can be applied constantly but are situational as not ALL targets on the board will be under their influence at ALL times.
- SI: (Wither 5%)
- SW: (Sonic Barrier Value Unknown)
- BH: (Combust 4%)

Shield Chance
For the purposes of simplicity we are going to assume a GlanceRating of 0.
- SI: (Shield Base 5%) + (Stance 15%) + (Dark Ward 15%) = 35%
- SW: (Shield Base 5%) + (Stance 15%) + (Shield Specialization 4%) = 24%
- BH: (Premium Shield Base 5%) + (Stance 15%) + (Shield Vents 2% + Empowered Tech 10%) = 32%

Shield Absorption
For purposes of simplicity we are going to assume a AbsorptionRating of 0.
- SI: (Premium Shield Base 20%) + (Hollow 4%) = 24%
- SW: (Premium Shield Base 20%) = 20%
- BH: (Premium Shield Base 20%) + (Ablative Upgrades 6%) = 26%

Avoidance: Ranged Deflection & Melee Parry
For purposes of simplicity we are going to assume a DFR of 0.
- SI: (Base 10%) + (Premonition 2%) + (Lightning Reflexes 4%) = 16% or 21% w/Discharge
- SW: (Base 5%) + (Guard Stance 6%) + (Blade Barricade 6%) = 17% or 22% w/Smash
- BH: (Base 5%) = 5%