What! I remember that i could only use one at a time back in magic farm 2 ?!
Also, once the well of suffering is being supplied by enough witch spawners, there is little problem having enough life essence for crafting. If anything, my main problem is getting enough blood shards for the armor.
By hand it has always been one but with the hopper or most item pipes (probably golems too) it can have up too one stack of a given item insterted in it at one time.