I'm guessing that they start at 250 skill, because the mats used/ picked at that kind of skill matches the mats that DK can encounter at their starting lvl. (ex: Plaguebloom, Thorium ore, Runecloth, Thick Leather)

We also guessed 200-250. But what if you drop Leatherworking for Smithing? Do you get to start all professions at 250, all the time? That would definitely be the toon on which to try out new skills. I wonder if too many people would QQ? Of course, they'd also be generally complaining that your Death Knight started at level 55 in the first place, and you've obviously played for a while to have your other 55+ character to qualify, so maybe that's ok.

I see the best solution is that your first two professions will start at 250. Then if you decide to respec, you have to go from 1-450 like everyone else.

its not like 0-250 costs very much anyways.

A bigger question would be if Fishing would start at 0 or 250. You can level fishing from 0-450 in SW, so the same argument for a profession like mining.

The biggest question is always exploiting. Is it unfair for people to start a DK just to pick up Mining and Skinning? and only level hi to 70?

I say no, but thats s decision for blizzard

on the other hand, it'd be kind of AWESOME to see a bunch of death knights picking flowers in the nubbin zones...

No, even a level 70 that drops his trade skills starts at 0. IF the DKs do get any main professions started at 200-250, it'd probably be the first 2 that s/he chose.