How about, instead of getting rid of the diorite pick, we update the functionality? Instead of giving diamond ore, what if it instead had the chance to drop resource from the other overworld ores, but proportionally? Essentially, if you used this pickaxe, it would allow you to mine like normal, but with the benefit of acting like diorite is being swapped out for other natural resources.. It also matches more closely with the theme'ing of the wilderspade.

This has a few other added benefits since it can't be used as targeted.
    - I can work with ANY diorite, even player-placed since you can't target specific ores easily.
    - It can have mending and be a persisting item without breaking the economy.

For those who don't want to read the numbers below, the change i'm recommending would result in the following resources for an entire chunk, bedrock to build limit:
    - 2 stacks of coal,
    - 1 stack of iron ingots
    - 9 gold ingots
    - 108 redstone dust
    -  8 lapis
    - 2 diamonds
This can of course be scaled, but it's intended to mirror normal mining results.

For those who want to see the math:
Attempted total block spawns/chuck (from Minecraft.Gamepedia)-
    - Diorite: 330
    - Coal: 340
    - Iron: 180
    - Gold: 18
    - Redstone: 64
    - Lapis: 7
    - Diamond: 5

Adjusting them based upon how much they drop, you'd average this many of each resource assuming no fortune enchant and everything was generated perfectly:
    - 340 coal
    - 180 iron ore
    - 18 gold ore
    - 288 redstone dust
    - 45.5 lapis lazuli   
    - 5 diamonds

Since there are about 330 diorite per chunk, let's say that we make 50% of them drop other resources. If kept proportional, the rates would look something like this:
    - 19.4% chance to drop 1 coal
    - 10.3% chance to drop 1 iron ingot
    - 1.03% chance to drop 1 gold ingot
    - 16.4% chance to drop 1 redstone dust
    - 2.6% chance to drop 1 lapis
    - 0.3% chance to drop 1 diamond
    - the rest of the time, it drops nothing (not even the diorite block)
Some of them should be adjusted to give multiple at a reduced rate (like a 4.1% chance to give 3-5 redstone dust instead), but the general values are the same.

The theoretical yeild should look something like this:
    - 64 coal
    - 34 iron ingots
    - 3.5 gold ingots
    - 54 redstone dust
    - 8.5 lapis
    - 0.9 diamonds
Based upon using some distribution checking on another server, it appears to be about twice that for a single bedrock-to-build-limit chunk, and would yield 2 diamonds per chunk, among the other items. Of course, these needs to be tweaked some based upon actual world generation and preference, but based upon my quick checks, if you take an entire chunk from build-limit to bedrock and mined it down using this pick for every single diorite, you'd end up with (on average) twice what I listed above. Which is two extra diamonds, and a lot of other random stuff. At that point, we could probably even increase the rate without issue.

Thanks for reading this far. I know the numbers aren't perfect, but hopefully the idea is close enough to something you all would be willing to support. I'd hate for this pick to be discontinued as I really enjoy the concept. 

This does sound like a good idea, the numbers just make it so confusing to read lol, but it all looks very good.

Those numbers seen complicated but I see exactly what you mean. I think this idea is a very good one. Hope redbau sees this!

Not gonna lie this is very great (and as math is something i'm kinda good i do understand the numbers :P). A good way to make it more balanced, neither too OP nor useless :]

Can you post the link for block generation attempts per chunk? I'm having a hard time finding it. Based on your information, getting a diamond ore block in a chunk of diorite converted using the WilderItem is only 3.3x more likely, which is not a huge margin by any means, considering the rairity of diamonds to begin with. It's possible that a simple rate adjustment would be all that's nessaccary to bring the odds in parity with the odds of diamonds, but I feel that conflicts with the overall spirit of WilderItems in general.

Tolcum:

They're all taken from here.
https://minecraft.gamepedia.com/Minecraft_Wiki

I tried to base it off those numbers for the theoretical, and then used //distr from World Edit to compare it to actual generation, using a sample size of 80 chunks to determine my final numbers. Thankfully, all of the rates can be multiplied and tweaked very easily, so if this gains more traction I can do a lot more analysis into actual resulting world generation to help balance this further.