I see nobody seems to be pairing bushi with any mage jobs, is it not good to keep them in mystic armour?
Part of it is Bushi is probably the best overall endgame DPSer. But for that, it should have Adrenaline and Focus which increase your DPS when HP Critical or 100%. Also, with Mystic Armor and just Battle Lore 8 (each BL is +1 STR and it goes up to BL16), Bushi + Mage will have trouble reaching STR 99 and especially trouble while also keeping your MAG high too.
The MAG is tempting to utilize but you have to consider opportunity cost.
Just because your BSH can be good at casting spells, it doesn't mean that's the best way to spend your time in combat. You could have someone else using their 99 MAG to cure; BSH could be using Masamune to DPS. So, that's why KNI and MNK are popular choices. You get some basic cures/buffs to help out and utilize the high MAG, but primarily it's for the extra BLs to reach 99 STR, Adrenaline and Focus for DPS, and then better shields or HP to keep your DPSer alive and DPSing.
That said, it's not
that big of a deal. I mean, if you really wanted your Mage to wield a katana, you can make it work. Lots of people beat IZJS without Bushi character and instead with a Foebreaker or Monk or even Knight with Tournesol for DPS. So, if you wanted a MNK with Whale Whisker or KNI with Tournesol (both within 2-8% of BSH DPS generally) you're main DPS, and then use BSH on something like a MNK/BSH 'healer' that focused on mostly combing the MNK's Curaja, Bravery/Faith, Arise, and Renew with the BSH's 99 MAG, you're going to be a pretty good healer -- you'd likely want your 3rd character with Channeling 3 and at least Cura though to help out with burst healing. Plus, that MNK/BSH could easily rotate into 2nd DPS and to pretty good DPS with still having 99 STR, Genji Glove, no Berserk, but probably often using Focus.
Or maybe you wanted an a support Mage Bushi... Combining, say, TBM and BSH. You're going to be a capable support character with Bubble, Berserk, Haste, etc. You'll probably need to focus on MAG while leveling but by endgame Hunts you'll be buffing strongly and accurately. Also, Channeling 3 let's you also do minor but quick burst healing [e.g. if HP Critical] because TBM can cast quick Curas in emergencies while your main healer (e.g. WHM/MCN) prepares Curaja or Renew (and they can focus on healing because your TBM/BSH takes care of buffs). And, while supporting buffs and minor burst healing, a TBM/BSH is still going to have 99 STR (or even probably 99/99 STR/MAG if you had 2 characters with BSH and your 'mage BSH got stuck with 2H Masamune) And, even without Adrenaline or Focus, you still have maxed stats, Swiftness 3, and Genji Glove, and any Masamune with that is -- even between buffs and burst healing -- is going to be decent enough DPS to support a separate primary DPS character and a primary healer.
Soooo, basically it doesn't really matter as long as your party all together is build sufficiently? Just pick a job that you like and fit's the character.
Most sort of 'inefficient' builds really only begin matter during Weak Mode (Lv1) playthroughs.
I mean, there can be a difference. There's one big optional boss fight later. The difference between a BSH/KNI on Basch and BSH/TBM on Penelo, you're probably looking at 2-3x as much damage, which could mean the difference between 30 minutes and 1 hour. Moreover, something perfectly tailored for that fight using the best combo rate and best elemental weakness could probably do that much DPS in 15-20 minutes.
But that's one fight. There's maybe a few fights like that, total, none during the main story, all optional Hunt Marks or Trial Bosses. And even then, you're going to have other characters doing damage, and vast majority of even the difficult optional bosses in the game take less than 30 minutes, so you're looking at maybe 5-10 minute difference (or dying and having to level up 5-10 levels more haha). But you're still going to eventually kick its butt.
It's only really the NewGame+ 'Weak Mode' (you're permanently stuck at Lv1) where optimization really begins to matter a lot. But even there, other things like utilizing creative use of items, knowing where all the 'early strong' weapons are, and even things that aren't as great in normal mode (e.g. guns) also matter. If you're creative enough with things like items, reverse, decoy, guns, getting weapons like the flame bow or some of the FF weapons as early as possible, etc, you could probably still even beat Weak Mode with some pretty average optimized builds. I'm not sure you'd want to do it with purely TBMs hahaha but as long as you got a clear cut DPSer, healing, and buffer, and one of those can tank, you're probably going to be able to find a way -- especially if you google an item faq. There's quite a lot of creative ways to 'break' the game and they'll help almost any build in Weak Mode.
I'm uncomfortable making such a huge decision as the job thing before knowing anything about the game.
What is the least important physical attacker job I could put on vran until I unlock the characters I want to use?
Really, if you were none the wiser from reading forums, you'd be happy with almost any party build as long as you have some sort of basic damage, healing, and buffing, which you're pretty much guaranteed to even accidently make with 12 jobs across 6 characters hhhh.