Final Fantasy XIV: HOW I MINE FOR FISH?

This morning I was looking up how to make an item I need to level up multiple crafting classes. It's a type of leather made by a leatherworker, but it is made out of two items you can't buy from vendors. One item appears to be a drop from two monsters in the game, but I know where those are and there seemed to be plenty of spawn points so I could just go farm those guys. The other item is found only by mining in a level 17 area. Ok, looks like it's time to try out the mining class!

Mining is different in this game compared to any other MMO gathering skill I've seen. Normally when you're out mining you find a mining point, you click on it a few times, you get some random stuff based on the type of point, and you repeat. In FFXIV when you start mining a window pops up listing all of the things you could get from this point along with the odds of getting the item, the odds of getting a high quality version of the item, and the level of the item. Then you get to pick which one you're trying for. Do I want an 84% chance at a zinc ore or a guaranteed lightning shard? I can buy the ore from a vendor (all low level crafting materials are also vendor bought, so low level mining is really worthless) but not the shard. But I have hundreds of shards, and the shard is only level 1. The level matters because the amount of experience you get from mining is determined by the level of the item you mine up. And since everything I can mine is worthless I might as well be maximizing my experience gain so I can reach the point where I can mine in the level 17 area.

Complicating matters further is the fact you get to try 4 times at each node. You get a experience chain bonus if you succeed multiple times in a row at the same node. Failing is not only worth no experience, it resets your chain. On top of that, I have an ability I can use to increase the odds of success for the entire node. I have a limited resource to spend on this ability that recharges slowly so I can use it on maybe a third of the nodes. The one I have right now adds a flat 15% to all of the odds of getting a regular item, so if I use it on the above node I'd be at 99% to get a zinc ore and 100% for everything else.

My gut feeling so far has been to go for the highest level item with a higher than 90% chance for success, but I want to quantify things a bit better than that. Could it ever be right to change items in the middle of a node? Take 3 hits of tin ore to build up my chain and then risk it all on a 84% zinc ore? The reason I think that might be the case is failing one of the initial three hits costs me experience on the last shot, but failing that one only costs me the experience for it alone. But first I need some base numbers for experience earned. (Note that until I hit level 10 I get an experience boost from an item I got for buying the original game.)

It looks like I get +4% experience for the first chain, +9% for the second chain, and +20% for the third chain. Base experience for the different items above when I am level 8 are 26, 77, 86, and 91. The level 1 item is right out. But I went and made a spreadsheet with a 16 row truth table showing the values and odds for each possible outcome. I made it so I could vary the item I went after each try if I wanted to, and got the following results:

4 zinc ore - 385xp
4 soiled femur - 392xp
4 tin ore - 382xp
4 lightning shard - 133xp
3 femur, 1 zinc - 391xp
3 tin, 1 zinc - 384xp
4 femur, buffed - 441xp
4 zinc, buffed - 462xp

At least for these specific items it doesn't make sense to vary the last item. I should be going for the same thing all the time. And that thing should be the soiled femur if I can't put up my buff, or the zinc ore if I can. Pretty close to my gut feeling. I was slightly overvaluing the consistency of the tin ore when the lowered experience makes it not worth the safety. Good to know!