Question about Wirt

Hello, everyone. I am new to this forum (not to diablo nor this mod. I am just curious about the items that wirt has for sale. It just never seems that he ever sales good items. I usually do the shopping in hell difficulty. My question is that does difficulty affect what wirt has to sale? If it helps, my character is level 39 mage who has killed diablo in hell (But never without disabling the ending movie).