For anyone with a character high enough to create a DK, the couple hundred gold it takes to get any skill to 275 fairly quickly shouldn't be too hard to get. If anything, it gives lower level characters (if there are any left that aren't alts) a good chance to make money off of the lower level mats.
For the gathering skills, a couple of hours in the newbie zones shouldn't be that bad either. I tend to to it that way with all my characters now anyway. After about level 20, you can easily outlevel your skill, so I tend to have to go back and power level the skill back up when I get bored at 70. Mining in particular got much easier to get up with the changes to smelting trivial levels, too. Now you can buy your way to about 200 (give or take, it's been a while) and just sell back the bars at a minor loss. The only one that will not likely be high on people's lists will be skinning/leatherworking, which don't really fit with the DK anyway.