Personally I think the MD and PD stones could be useful but I get enough people asking for my advice on whether to use PA or DC because they can't do the maths (it's not as simple as just looking at your current DC and deciding if it's over 1000), I think simplifying it by making them into set amounts of MAC/AC. So instead of 1% as it is currently or an increase to 2%, make Chrysocolla 40-40 MAC and Citrine 40-40 AC and while it wouldn't necessarily be much of an improvement over the current 1% (would actually be less for most high level people) it would make it clearer for people to see exactly what they are getting.
- - - Updated - - -
Also my thoughts on the Angelite stone, this could be very useful as it is, i.e. you could build a really powerful "vs undead kit" and I think people would do it, if only it was clearer what mobs are actually undead. There's plenty that can neither be tamed or turned by wiz, which sometimes makes it hard to tell what such a kit would work well on and nobody is really that keen on investing significantly on an experiment to find out