Alrighty, you requested HUDs of people who play multiple classes, so here's my wall of text contribution. - http://imgur.com/a/pGVfy Note: I use the Logitech G600, so I have 12 thumb buttons available to me. Those are the hotbars on the far right.

1) WHM

I don't really play WHM all that much, so my layout probably isn't ideal. I have the 3 Cure spells in order, Esuna on 4 and Regen on 5. I didn't want Hotbar 1 getting to cluttered, so I moved Medica I and II to the Ctrl + x keys.
Cleric Stance on Q for easy stance dancing.

2) SCH

Because SCH has less heals than WHM, I put them all on hotbar #1. Physic, Adlo, Succor, Leeches.
I tried having the DoT spells on my mouse, but I hated it, so I put them back on the numbered hotbars. Cleric Stance on Q for easy stance dancing.

3) SMN

I don't play SMN, I threw this together in about 30 seconds, so pay no attention to it.

4) BLM

I like having my Fire and Blizzard spells in order, it just makes it easier for me. I rarely use Thunder II, so I just removed it from my hotbar.
Like all my layouts, I put self buffs and oGCD things on my mouse buttons. Transpose and Convert on Q and E for ease of use.

5) BRD

Easiest hotbar to setup.
Q for easy Bloodletter access, CTRL keys for AoE. Nothing special here.

6) MNK

My main class.
I put my attack skills in form order, so when pulling off a rotation, it goes in sequence depending on what form I am in.
CTRL keys for oGCD attacks and ToD. Q for easy Shoulder Tackle, F and G for potions.

7) DRG

I no longer play DRG, but this is what my layout was before I quit playing it. Usually my oGCD attacks would be on my CTRL keys, but I prefer the jumps to be on my mouse for DRG.

8) PLD

Not really much to say here, I guess. 1-2-3 for Halone, 1-4 for Riot Blade.

Only things worth noting are my easy access to Shield Bash, Shield Swipe, Sword Oath and Shield oath. With them being assigned to Q, E, G and F, respectively.

9) WAR

Again, same as PLD, nothing of note here.
Only thing is my ease of access to some of my main skills.
Stun, Inner Beast, Infuriate and Defiance, all are near my WASD buttons, very useful.

10) MRD

I play MRD a lot, so I included my MRD setup as well, it's similar to my WAR layout.

11) Other

Put some boxes here to show where my other HUD elements go. I hate having a cluttered HUD, so I can never put anything in the center of the screen like some people do.

I have all my classes and jobs on the hotbars on the far right. Notices appear just to the left of them (Next to the GSM icon)