I probably wouldn't pay 1 DA for 15% physical mitigation, especially when both TBN and Grit individually give greater DR for a lower net cost. As it is, I'd have a lot of trouble justifying DA DM in 4.0 for the 30% DR outside of multi-hit magical tankbusters, given that TBN and baseline DM usually give you more mitigation for a lower net cost on a single hit. I like Brannigan's suggestion from earlier in the thread about turning DA DM into raid-wide mitigation.
Shadow Wall doesn't do anything exciting, but it gets the job done. The only real way to improve on it is to either lower the recast or have it reflect damage, and the former is overkill with TBN. I feel that with the addition of Rampart to WAR, Vengeance is overtuned, so it's not really a great point of comparison. The main problem with DRK's mitigation is LD, which needs to be flat out reworked so that it doesn't arbitrarily penalise your healers. Both Hallowed and Holmgang are vastly superior for different reasons.
Blood Price is odd. Even if there's nothing actively happening (i.e. phase transition/animation), you gain 4 blood per tick so long as you're in combat, netting you about 20 blood. It's not worth swapping to Grit for, but if you are in Grit during a phase transition, it's basically free blood. It even seems to tick up while you're doing an ATE, such as Susano's sword. I think part of the problem is that they tuned it based on tanking multiple targets (you gain 0.05 DA/tick as opposed to BW's 0.2 DA/tick), so it tends to be a bit underwhelming against a slow hitting mob in single target. One possibility could be to remove the MP regen penalty of Darkside with it active, granting you 568 MP per tick passively. This would let you use it similarly to SAM or MNK's meditate ability during in-combat downtime to restore MP and blood. I don't think that simply adding DR to it will make it see more use, however.
As far as self-healing is concerned, the best solution is to allow Souleater's lifesteal to function out of Grit as well (or at the very least, let it function under BW). This not only removes the need for a Clemency or Equilibrium equivalent, but also offsets some of the passive DR advantage that PLD has from block. DA AD is extremely expensive healing (1.4 DA), and using it in single target as a self-heal seems to go against the spirit of its use.
I understand some of the concerns about DP, but I don't think that people are necessarily thinking about it correctly. Efficiency matters only in sustained encounters where you run the risk of running out of MP. Most AoE situations often are shorter, burn-orientated encounters which have you running a surplus of resources (i.e. you gain it faster than you can spend it). Potency per unit time is much more important than efficiency in these situations, because any MP gains when you're at cap are wasted. The main problem with DP is that there really isn't any situation where you'd want to use the baseline ability without DA, because it fits neither of those categories. I think they'd be much better off creating an MP efficient but low potency baseline DP for use in single target, and keep DADP as it is for use in multiple target/burn phases. Alternatively, just bake the DA cost into DP for simplicity, if there is nothing to be gained from the baseline ability.