Do a dweller's level or SPECIAL values affect how effective they are with weapons?
I know this is the case in other Fallout games, but am I wasting my time training up my dwellers in Agility and Intelligence in order to better wield the weapons I have acquired?
Agility and intelligence are probably a waste of time for dwellers who won't be exploring the wastes.
The only difference based on level is the dweller's total hit points, and the cost to revive them.
However, there is some thought that some of the SPECIAL stats affect combat. (see this question and the links within the answer). Strength may increase damage (though it's not certain this applies within the vault) and perception may increase aim/hit rate and thus overall damage.
In the wastes, success against a specific enemy type seems to be influenced by a specific stat (excluding endurance which seems to be a purely defensive stat).
Personally, I'm training the primary stat and luck for my stay-at-home dwellers, though I'm phasing out diners/gardens and water production as I introduce more Nuka Cola bottlers. As my vault improves I'll have an excess of workers, so I'll try to train everyone in endurance and possibly strength/perception. Wasteland explorers are being trained across all stats.
Weapons stats seem to matter most on quests and and wasteland exploration. There matching SPECIAL skills and weapons seems to increase weapon usefulness.
On a side note, all SPECIAL skills matter in the vault not so much for weapons but for manufacturing. For example, if you're making an S weapon, you can reduce manufacturing time by 60% by having all the workers have a maxed out S level. Same for very other manufacturing room. The more maxed out workers you have doing the job, the quicker it's completed. So, all SPECIAL skills are necessary.
