Part of what makes 'fun' class to play is the interactivity. DKs have a lot of that going on.. keeping eye on your runes/diseases/runic power. When playing single player this makes DKs a lot of fun to play.. but as a boxer your attention is split between tanking/dps/heals/movement and it makes it more challenging. You can still do it but it's not as hands off as a pally. Generally once you get your rotations going, it goes ok but once you miss things or the diseases falloff it's when DKs effectiveness drops. That and I've heard some issues with disease immune bosses that could make your life harder. If you play one with a simpler rotation dps class like a shammy it will be a lot easier than if you play it with 3 (affliction) locks and a druid.

I personally really enjoy healing on my druid but for boxing I stick with either a priest or shammies. I can use my druid but his effectiveness drops as I can't manage as well stacking lifeblooms/hots while boxing. I do plan to roll a DK as I have 4 priest that are 55 so they're perfect to level with it. The setup will be fun but I'm not expecting it to be as easy as my pally/shammies setup.