I dont know how much of an issue this really is. I craft a lot and most of my full stack purchases are for bulk crafting and can shift full stacks fairly easily a lot of the time.
A lot of the time large stack sales are items that are used in many recipes, levelling, or are base incredients crafters use a lot. Like, who buys 10 Alumen? If you're a leatherworker you need a ton of the stuff.
Also, there are usually smaller quantities of most items on the boards, particularly at peak times. Its quite rare not to have buying options.