I am interested in starting a DK. Since DKs start @ level 55, I was wondering if there are higher DPS trinkets available in the AH than the heirloom trinkets available? I'm going to get all of the exp gain bonus heirloom, but if there's better gear that I can spend gold on, then I'd rather not farm justice to get things like heirloom and a 2H weapon for my Unholy DK.
There are very few BoE trinkets, so not much can be auctioned away.
Darkmoon Card: Maelstrom is the prime target, usable at level 60 and may last you a while. It can be acquired for quite cheaply if you're in luck as well.
Sonic Booster is awesome if you're an engineer, but is limited by that.
The final option, Mercurial Stone is a prime option from level 65 and on. You can use two of them as they are not unique, and hit rating is a great DPS boost as you level if you're fighting enemies the same or higher level than you.
After those, there are Darkmoon cards available at level 70 (some of them are a definite upgrade) and a fair few more at level 80.
Overall I would just use the heirlooms to be honest.
I am not aware of any heirloom trinkets that are good for DPS DKs. The best of the four Swfit Hand of Justice, only gives 17 haste at 55.
There aren't a lot of Bind on Equip trinkets that can be sold on AH in the first place, let alone that fact that it depends on which realm you are on.
The way to get good starting DPS trinkets is through running dungeon instances and completing quests in the Outland. For example, completing this quest (assuming you are Horde), will get you this and complete this quest will get you this. This is by far the best way.