Paladin guide to drk cooldown:

Dark Rampart = Rampart
Dark Sentinel = Sentinel
Dark Holmgang = Hallowed Ground
Dark Dance = Fish for Reprisal when you want it; just make sure you use it
(DA)Dark Mind = "If I was a paladin I'd have to use Hallowed Ground here" Top priority move for magic stuff since it gives you ridiculous freedom with dark rampart and dark sentinel.
Everything else is crossclass. Don't forget to Blind/DADA when tanking dodge-able monsters (dungeon trash, A4S adds, probably A2S)