The lootdrop table entry is what I was missing. Thank you! That seems like a pretty useless table, but apparently it's significant. My first HG kill dropped the scepter as expected. Thanks guys!

Hmm, I would like to add defiant gear to most of the mobs, but since the loottables are loaded globally, I fear that memory usage will explode.

Will there be a problem if there are too many long loottables and if so, is it hard to make loottables load per zone instead?

No one knows?

You could do it with georges' d2 loot editor. Get the ID's for the tier of defiant armor you'd want, plug them in the custom item list, and set the appropriate level range. Play around with the values, as you'll need to run it a few times on each level range (so keep the % of mobs to drop loot low).

Well, I know how to link the defiant gear to the mobs loottables. My question was if it will have a dramatic impact on the memory usage if I add defiant (or other missing gear from ZAM) to most of the NPCs.

Never really paid much attention to the amount of memory being used after adding loot tables but if there is some change it should be negligible. If you are really worried about it then backup your db then make the changes and see what happens.