Expertise vs Haste vs Armor penetrationFollow

Ok, I need some help. These three things greatly confuse me.
I kinda get the general idea of what they do, but I'm not exactly sure as to how each would effect my character.


It would be much appreciated if someone would run through these 3 things for me, and explain where they would be the most beneficial and least beneficial for a rogue. (Other classes too if it helps make the point, but primarily how they effect a rogue.)

Most of the sites I've seen give highly technical explanations of what they do to dps and my head just can't make the connection between the numerical values of each stat and the actual way each one works.

In short: Dumb it down for me, and bonus points for explaining any synergies there are with each particular effect.

Thanks!

The problem with comparing armor penetration to any other stat is that armpen is not a constant dam increase. Meaning the more armor a mob has the smaller the effect of your armpen.

In other words armpen will greatly increase your dam on low to lightly armored mobs, but have a smaller dam increase on heavily armored mobs(plate wearers for instance).

So saying x armpen = y other stat is problematic since armpen will give you a different increase in dam depending on the mob's armor, what armor reducing debuffs are on the mob and how much armpen you have stacked(executioner, serrated blades, armpen gear). And even more problematic is the situation where you have stacked too much armpen as the stat is no gain to dps once you reduce the mob's armor to 0.

The main synergy between the 3 stats, armpen, haste and expertise is +hit. None of these stats mean crap if you don't hit, only thing you will do it miss faster and harder with fewer dodges. For combat builds haste and expertise have the most synergy as combat potency and wpn expertise should be part of your build. Armpen has synergy with serrated blades which means trispec hemo or other sub build.