Okay, here's the deal. I've been thinking for quite some time about how the damage and penetration mechanics work together against armoured targets. So far, I don't like it. I want to illustrate this example with power armour.
Now according to the fluff, power armour litteraly tend to completely shrug off damage from certain small arms fire (like lasguns and autoguns). In Dark Heresy, power armour have an AP value of 8, which is the highest amount of any kind of armour (save for best craftsmanship power armour which would have 9).
Now lasguns and autoguns do 1d10+3 in damage. The average result would be 8, which of course wouldn't penetrate power armour. But that's when everything is standard and nominal. Once you start to break out firepower that is a bit more heavy (heavy but still not anti-tank that is) even power armour can seem quite whimpy. Especially when talents and armour pierceing ammunition is involved.
It seems to me that what provides the most protection most of the time isn't exactly any suit of armour, but rather a high Toughness Bonus. I don't think that makes much sense. If you actually feel the need to create a powered, full-enclosing exo-skeleton then obviously you must be of the opinion that the constitution of the wearer will be quite frail against some weapons.
What I'd like to see is a more tactical rules set in how damage and penetration works in correlation with eachother. Sometimes, certain weapons can do ridiculous amounts of damage in one hit, but not have much in the way of a penetration value at all. But at certain levels of damage, penetration will simply be insignificant, because the damage is more than enough to nullify any effect a set of armour could have.
The thing is, im not sure of how to rectify this. The first thing that comes to mind would be that remaining AP, not nullified by Penetration absorb more than just one point of damage for each hit (perhaps absorbing 2 points of damage, or even as much as 4).
That way you would have to use a weapon with suitable penetration capabilities against armoured targets, rather than just sticking with the one that does the most damage. But im afraid that doing these changes would have other rammifications that I've yet to consider.
Please, share your thoughts. But refrain from flooding the thread with "Well, I kinda think the current system is good as it is"-types of responses, because as genuine as they might be, they don't really help in adressing the issues im concerned about. Thank you!