Good questions, I'll answer them in turn as best I can.
I think as for how many characters it would be ideal to have, I reckon that is up to the individual and how much time they have. Personally I will have one and level all the jobs I feel like playing on the one toon. However, some people like alts and want a variety race wise, so may want to level more.
Disciple of War vs disciple of magic, again is down to how you like to play. I like ranged caster dps and healers, so I will level a CNJ which will become a WHM at 30. (I will have to grit my teeth and level a GLD to 15 to allow me to do the WHM quest, which will be funny as I hate melee!) As a WHM is primarily for single target heals, I will also try out scholar eventually as well, so I can switch depending opn whether we need tank heals or raid heals.
As for gear, at low levels my CNJ and WHM can often wear the same gear, but the MND stat is my CNJ's primary whereas the INT is better for my THM. So as I get higher, the gear will be less interchangeable if you plan to min max.
There is nothing wrong with having both your Hyur and Mi'qote, it just means you cannot out of combat switch to a different job on the fly. For example, if I am running an 24 person raid and 5 healers show up and we are short on dps, we can switch between us to optimise the group. Or you might just feel like a change and be bored with healing and feel like rawwwring it up with a little dps.
I guess your question illustrates the point that you can do whatever you feel like and there really is no right or wrong way of doing it, it is going to depend on how you like to play and what you love to do at endgame.
Edit : A coupla things to consider:
If they make BOP crafted items, that I have the right crafting job levelled to benefit the right toon eg weaving for a DOM alt (another reason I decided to level them all on one toon). But then I also do not yet know if crafted gear is BOE or BOP.
If you play a THM for example, you can level an CNJ and use a certain number of abilities on your THM. My THM is 18, which allows me 3 slots to use from my CNJ abilities. So my THM (mage) can use Cure, Protect and Raise (Rez) as well as her magey type spells. Which is win. That of course would not be possible if I had levelled them on separate characters. (The higher you level, the more slots become available to you from classes other than your main job you have levelled.)
» Edited on: 2013-06-29 21:18:41