I understand where you're comeing from Ualaa, but I would still choose DK over Paladin for a pure tanking role and here's why:

1. DK's have more AE damage. Unholy will put two damage dots on one mob, spread them to every mob then drop Death and Decay and Unholy Blight. In my experience so far the damage is almost that of a Mage's AE'ing. This directly translates into threat.

2. Ebon Plague. This to me is the number one reason to pick the DK over the Paladin. 13% more damage for your group across the board is the best buff that a tank can bring to your 4 Shaman.

3. You have a 30 yard range taunt that pulls them to you, an 8 second cooldown melee taunt, and you can macro your ghoul to leap at the target and stun for 3 seconds. Not better than a Paladin, but comparable.

My tanking rotation looks like this: I pull a mob with E (Ranged disease), then put my second disease on the target (F), then spread those disease to all the other target (R). Then I put up Death and Decay (Shift+R). My DPS button is the spacebar which does a castsequence on my Shaman and it automatically does the +threat strike and Unholy Blight for my DK. You're talking about basically four buttons to make my DK tank work. Shift+Space heals my DK and Control+Space heals my group. With this setup I can focus very easily on tanking.

I'm not saying it's as simple as spamming one castrandom macro, but you get tangible gains for putting in just a little more effort.