I love the current PP and AD; they both look worthwhile and much, much more balanced now!
Nice. You've come up with some really neat stuff here, and it's much cleaner now you've incorporated the suggestions above. My only minor point of criticism is the level 16 power - I could be wrong here, but can't think of any creatures that are immune to necrotic damage. So I'd just strike that out, and keep it focused on resist.
Lastly, the level 26 power brings in "favor points". Now, I love little add-ons like this, but if you're going to use a completely new mechanic like that, I'd prefer it to be hardwired into that class/PP/EP somehow. Perhaps you can sacrifice healing surges at any time to gain a point of favor, or something. Anyway, just a thought.
Favor tokens to demonic runes is cool by me; I made up "favor tokens" because the original version had an unnamed resource, and it made a lot more concrete sense to name it in some way.
Ok, the ugly: I think the power level of the PP is more or less right -- but I do have an issue with how all over the map it is in terms of what it encourages in terms of your base character. I mean, you have:
F16: Necrotic damage, Abyss keyword (only exists in this PP, maybe in your related class)
U12: Melee Basic attacks.
Attack powers: Implement
So, what you're looking for is a class that mostly make necrotic melee basic attacks, but uses an implement.
That's what? Hexblade? Maybe Executioner Assassin with a Shadow Master Ki focus.
I'd probably:
Make the U12 affect all attacks. It's a daily -- a global damage buff is appropriate.
Make the F16 affect all necrotic attacks. At 16th level, you're not that far from getting the crit optiization available at epic levels; getting it for necrotic classes at 16 is fine.
That way, it ends up being a PP that boosts necrotic damage for classes that can use an implement and are (or can multiclass to) Arcane -- which is a perfectly reasonable set of requirements.
No you didn't, at least as it is you have it back to melee 1 or ranged 5, with the charge. Frankly, I think you should leave it like that; it's a nice demi-feature; particularly with the PP reighned in, and doesn't hurt classes that take it as a ranged boost.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.