I would tend to say, threat is now mostly from damage dealt, and the DK is the highest dps of the tanks, so in a single target fight they're the best tank.

Against multiple opponents, the paladin has the best AoE damage, not specifically because of Consecrate which may or may not compare with Death & Decay, Thundershock, Swipe etc, but because of Holy Shield which causes a high amount of Holy Damage (threat) whenever the paladin blocks, which is very often. So, on the six adds who came with the main target, the paladin has exceptional threat via their basic tanking manuevers, and the same ability to pick up an add via their AoE move.

Paladin would be my top vote for a boxer, because of their ease of play. The fewer things you need to click to be effective, the more useful the respective tank is for a boxer who already has a lot of things to click. A paladin can be extremely effective with a "/castrandom Holy Shield, Consecrate, Hammer of the Righteous" macro. With a cast random, if an ability is on cooldown, the macro will not try to use it, so one button mashed and tied to your other toons main dps move results in effective tanking. True, you may need to adjust your positioning to avoid an AoE or break line of sight or move so a mob is not behind you, but that is true for all of the other tanks as well. The paladin has an aoe taunt, which is cast at a friendly and then taunts up to 3 mobs from them to the paladin, adding to their AoE supremacy. Pally buffs are very nice as well, and Hand of Protection is effectively a taunt vs taunt immune mobs, as an immune target does not interest mobs that much.

I'm not saying a DK won't work, just that any of the tank options will be fine for both single target pulls and AoE pulls... but the Paladin is an easier tank to multi-box then the others and is probably the best option for multiple pulls.