To clarify, I mean using a Whetstone Wheel. If you have multiple items to improve on a whetstone wheel, or on an anvil, you have to improve each one individually, even though it gives you the option of improving all of them at once. Clicking on Combine will show it going through the motion, but it doesn't actually improve any of them, not even the first one.
I primarily craft large amounts of armor/weapons simply to sell them, and improving them first makes sense since you get more gold. But while I can craft the armor in one batch, I can't improve them ;-/
