Yeah, that comment from Vastar really got us thinking, didn’t it? 
Here’s a response of mine from the other thread for context, as well:
I’d like to propose a somewhat counterintuitive alternative to your idea @Havok40k:
I think, say, a diamond (whatever) pickaxe should have less durability than its more common brethren. It’s an interesting gameplay choice if I have to juggle its fragility with regular use. I.e. my diamond pick is for mining rare blocks, and there’s some super-durable stone pick for regular blocks.
There’d still need to be be tiers of “durable” picks and “specialty” picks, 'cause progression.
Now that I stand back a bit, I guess I’m just lobbying for more item variation and “average” item durability to push players to consider trade offs between those item types.