There's usually lower level stuff on there.
What I do is when I find I'm having a hard time, get rid of your lowest level item and get an item of your character level in the auction house. Make sure you search for more than 5 minutes and get something with at least equivalent stats. Also, stick to a plan with how you use your character and get items that compliment that. I haven't played Witch Doctor past like 20, so I don't know many good strategies.
But, for example:
My highest is a Revenge barbarian (Revenge attacks all nearby enemies for health, but you need to be hit for it to activate). I have items to increase the crit chance of Revenge specifically and also have life steal and life per hit. I also need less dexterity, so I can be hit by attacks more often and trigger Revenge, and tons of vitality to ensure I don't die from those hits, thorns to damage the enemies that are hitting me. All of these things I need specifically from items.