Thump92

@Thump92 my bad. In my third brain confused lack of sleep, I confused Drain with Dispel. Dispel is how the Armor Shredding strike is written up. Though I can’t see why you can’t still do Drain vs rPD though. It might be like Backlash where it’s designed for one thing but comes in handy for another.
Oh and easiest way to change it in Hero Designer is to highlight Cha window and backspace to clear the characteristic then type in Resistant PD or rPD. It will show.

Now I know you can. It’s listed in HSMA. 

As a target? It can be done.
Why is it not seen? Well, this is conjecture on my part, but that would be due to efficiency.

PD and ED and DCV are all Defensive Characteristics. What that means for Adjustment powers like Drain is that they are twice as hard to effect. (6e1, 141) So what does that mean? Well, if you are trying to drain a Resistant PD, that's clocking in at an active point of 1.5 per point. So you need to drain 3 Active Points to drain 1 Resistant PD. Considering that one can expect to roll 3.5 on a d6, you are essentially getting 1 rPD per 1 Dice.

So that's a cost of 10 Points to on average, remove 1 point of rPD/ED. For DCV it's worse. You need to drain 10 points to remove 1 DCV. So, An average of 3 dice, or 30pt for 1 DCV removed. And that is all presuming you are okay with the points coming back at the end of the round

Yes, HSMA = Hero System Martial Arts.