Of late we have been forced to change our ideas about professions. It has not been brewing for a while but it really was an idea whose time had come. We foreshadowed this some time back about profession bonuses. Even we have not said to choose professions that help your toon but for making a profit.
   It is undeniable that this applies to the very serious gamer and not so much to the casual player. What is more you are going to have to get your mind around this one a little bit because it is going to make some of you frown.
There are two reasons for professions. The first one is because the use of the profession makes you some gold. The second is that having the profession is a benefit to your toon. For our part you could make the case for just liking it but that's a bit of a stretch in a virtual world.
Now, for the power player you have at least one toon with every available profession at least skill level 375 and most of the time it's going to take 425. In order to train to grand master you have to be at least level 60. So in order to have at least one of all ten professions you will need five level 60+ toons. This may be a big stretch for the casual player, but if you've got the time it also means you never ever have to depend on the AH again for anything except the odd BoE world drop you think you can't live without.
Not a fan of farming, you have at least got a miner, herbalist and skinner if you really need one. And the next is really going to bother some people, but here goes.
For your information, there are four Death Knights on your account as professions alt. The task of leveling an alt just for a profession went from something like 50 hours of work to about 3 with the Death Knight. You'll exit the DK starting area at around level 58 and then it's just a few rounds of goop in Hellfire to 60 and you're done with this dude forever.
In the game, you have now got level 60 toon ready for any profession with very little time invested in the process. Plus, and this is where it gets good, you have not committed yourself to wasting time on your main for anything but raiding.
Because they make your toon powerful, you should choose professions for your main. And at this point it's really hard to beat Blacksmithing and Jewelcrafting. Two extra sockets with those nice JC only upgraded gems is probably the best combo in the game, not to mention better gems in every slot of every piece of gear you wear.
You might also want professions like herbalism for the extra heal or something that goes well with PvP if that's your thing. Inscription is an option for the uber shoulder enchant if you don't want to make the Sons of Hodir rep grind.
The basic premise here is to give your main(s) the professions that give you the best buffs, and then just use a DK for everything else. This was never really a consideration before Wrath since professions didn't have great bonuses before. Plus you had to level a toon from 1 to 50 to even think about maxing skills in everything.
But with the advent of the DK and some really sweet buffs from certain professions this new way of Dominating can really save you a ton of time. So go get yourself a few DK's for everything you might have skipped and get your main toon a little extra pop for raiding.