Sometimes I get it when I've taken down shields. Other times it only pops up when I dent the armor. Is there an overall calculation taking in % of total eHP? How does this work exactly?

Ever use a Large Missile Turret on an HAV? You get like 75 vehicle damage wps for nearly ever missile.

It's my understanding that Damage WPs are awarded after you do a certain percentage of their total health. This can be confusing because say a vehicle has 4000 HP and you need to deal 25% of its total HP (1000) to get WP for it. If you deal 1000 damage and the vehicle isn't hardened, you'll get WP, but if it is hardened, you deal 1000 points of damage, but it resists 40% of it so you really only do 600 points, and thus don't get any WP.

In addition, since it's based off a % of the total HP, the fit will greatly determine at what point you'll get WP. For example if a Gunnlogi puts a lot of armor plates on, its Armor HP will be similar to its shield HP, and this you'll feel like you need to deal more shield damage to get the needed percentage to get WP, since shields only make up half of its total HP. However if the same Gunnlogi stacks on a ton of shield extenders and no plates, you'll feel like you need to deal less damage to the shields, since most of its HP is tied up in shields.