The batch I got looks right, but its very hard.

Its not cuttable by hand pruners at all.

Is this normal?

and

How should I shred it?

I can't remember who's advice this originally was, but, it was to freeze the bark and shred/blend as it's thawing. Consequently, helps with cell lysing too.

A cheap coffee grinder will work just fine.

From my experience, generally the thicker and harder the bark, the older it is. The older it is the more alkaloids will be in there.

I would NOT recommend a cheap coffee grinder, unless you feel like wasting your money. I've broken coffee grinders and high quality blenders within minutes of use with hard acacia...hence, I no longer use them. Powder is my preferred way now. A couple simple, easy hcl acid washes and then a quick reduction of volume makes for much less work.

You don't need to shred it, but you could do an acid wash with the bark..or boil, and then take the strained bark then put it in the freezer once it's absorbed alot of water, to help break up the cell walls. then do you boils again. You can also use hcl instead of vinegar.