I feel it/they should be recorded somewhere, but I agree not here.

https://ff14wiki.info/クラス
List of other classes in final fantasy 14.

N-gram Corpus Counts
╭─ーーー─┬───────╮
│ 格闘士 │ 2,708 │ - pugilist
│ 双剣士 │ 2,654 │ - rogue
│ 幻術士 │ 1,450 │ - conjurer
│ 呪術士 │ 1,361 │ - thaumaturge
│ 採掘師 │ 1,028 │ - miner (this entry)
│ 弓術士 │   715 │ - archer
│ 園芸師 │   621 │ - botanist
│ 剣術士 │   370 │ - gladiator
│ 槍術士 │   153 │ - lancer
│ 斧術士 │    22 │ - marauder
│ 巴術士 │     0 │ - arcanist
╰─ーーー─┴───────╯

None of the above (other than "miner") are in JMdict

I also think that these are probably too niche and too compositional for a general purpose dictionary

It's not really "rare". It's just not used in the real word (i.e. outside video games).
But it's not widely used in gaming either. It's a character class in Final Fantasy, which explains the reasonably high n-gram count. I don't think it belongs in jmdict (or jmnedict). This is a general-purpose dictionary, not a Final Fantasy Wiki.
Also, given that we have an entry for 師, the meaning isn't difficult to deduce.

I don't think that note improves on the entry. Better to just tag it as rare so that people don't end up using it from reverse searches.

@@ -12 +12,2 @@
-<gloss>miner (in games, esp. Final Fantasy)</gloss>
+<misc>&rare;</misc>
+<gloss>miner</gloss>

I was going to comment that given the number of WWW hits, it should be recorded somehow. It's not really a proper name - more a fictional occupation. The key thing is to avoid the impression that it's a synonym for 鉱山労働者 or 炭坑夫.

@@ -12 +12 @@
-<gloss>miner</gloss>
+<gloss>miner (in games, esp. Final Fantasy)</gloss>