The values are calculated by:
1) remove all aggro buffs, including hatred rune
2) find a monster you do not 1 shot
3) use skill X
4) immediately after, remove target (so you don't white hit the monster, generating more aggro)
5) re-target monster, and check threat/hate/aggro value (can use a macro or an addon to do this, the game itself only updates aggro list every 3-5 seconds so spamming it won't necessarily get you to-the-second accurate information)
6) divide threat by damage dealt
If done quickly, even with holy strike, you can see the aggro generated from the intial hit, but before any holy seal damage. Also note that this formula isn't exactly equal, but when you get 2.50045 when computing holy strike value, it suggests that there's a small variance in threat generated (like how dps skills do 50 001 one hit and 49 985 the next, perhaps aggro generated jumps). Also, once in combat, you generate 1 threat per 3 seconds or something like that standing around doing nothing.
WITHOUT Holy Power Explosion, holy strike has 2.5x, WWS x10 and TSB x1. TSB goes to x10 with holy power explosion (this x10 doesn't factor in the increase from the buff itself).
Total aggro done = (Damage Dealt) x (Skill Multiplier) x (Total +aggro buffs).
+aggro buffs add. A hatred X, Holy Power Explosion (+52.5% for calculation), and Threaten give a (base of 1 + 0.54 + 0.525 + 1.1365) x3.43 bonus (significantly less then multiplying 1.54 x 1.525 x 2.365)
Here we see that critting directly results in a 2.5 (more or less depending on rings) increase in aggro dealt, far greater then any single buff, even threaten. One reason why k/w is so strong, b/c it gets a huge crit rate increase from Quick Reflexes Skill. You can also see that more damage dealt = more aggro, so even a knight who does 30k crits benefits from using strong stm and any other dmg/attack speed buffs they can get (or patk buffs if you have enough patk for it to make a difference...see other threads about patk vs pdef ).
Skills that "increase aggro by 5%" do EXACTLY that. If you currently have 1 000 000 threat, using the skill will get you 1 050 000 threat.
Finally, when a skill says "aggro increase with skill level" what it really means is "the skill does more damage as you level it, which therefore means more total aggro generated". The multiplier, as far as i know, stays the same, but the Damage Dealt portion of the formula increases. Maxing skills increases aggro, but not by huge leaps and bounds (a 400%-->440% main hand dps skill increase leads to only 7% increase in aggro/dmg, not 10% which is the "skill increase").
This post has been edited 6 times, last edit by "BlankMinded" (Mar 24th 2015, 3:48pm)