Another over powering set of suggestions. DRKs have some problems but its not your potency as a class, or even your defenses. You have some strange theme issues and an issue with certain powers replacing other ones (Abyssal Drain/Unmend, etc).

You have an OT/MT debuff which Alexander has proven is quite good. Reprisal is just jelly WHEN you are tanking. Basically you get your rage of halone magic down and then reprisal which you can throw out if the target seems to use physical attacks (which is quite powerful). Its not meant to be parity for storm combos off warriors, since that IS their damage debuff.

You have weaker cds--yes, but you have access to far shorter cds. Dark Mind on 60 seconds. Dark Dance on 60 seconds?

Core potencies on your abilities are fantastic. Shield lob is 120. Your version? 150? Aggro combo on paladin is 240---on DRK? 300. Your damage WHILE tanking is quite great--better than either other tank. When it comes to off tank, you do not do as well as warrior (not even close--but warriors are amazing OT's) but you are still ahead of Paladins.

There are places you excel at, others you do not. You are not meant to have parity---look at Paladins. No real aoe, no real burst, no real mobility. They have plenty of downsides--and plenty of upsides. If you compare your weaknesses to the strengths of other classes (paladins--mitigation, or warriors and off tanking) then you will think you are quite weak, but are missing the point of looking at dark as a complete class. You have a tool kit thats quite good, and its obviously a first pass--but suggesting such massive over powering ideas are I feel, implicit that you are completely unaware of how other classes actually play and how OP you would be. Everyone would just be dark knights if even half of these suggestions went live--and that is not the sort of game anyone wants.