Bars 1, 4 are the main bars. Bar 1 for single target damage and single target healing. Bar 4 for multi-target damage and multi-target healing.
I try to keep the same category of ability on the placement between these two bars, so for instance, Regen/Medica II are on the same relative position as they both provide regen. The same with Cure and Cure II versus Medica and Cure III for non-regen heals.

Left Expanded XHB bar is for less frequently used heals with long cooldowns or heals that use a resource like blood lilly. These are also placed on a standard non-XHB bar visible at all times, so I can see their cooldowns even when I don't have it selected. The exlaimation point macro there is an experiment I'm trying which combines swiftcast with an all-classes raise. I've not had a chance to use it yet for all of them, so I keep it there alongside my actual raise ability as a backup.

Hotbars for Lv60 White Mage.

If it was possible, but it isn't. Too bad. I wish there was only 16 Instant/OGCd spells. -WHM with a bad left thumb

I try to move my index fingers as little as possible while playing. Nothing really on LTLT or RTRT because I fumble that input like crazy. My pointers aren't so great either it turns out.

Updated for Dawntrail

Buttons consistent for similar job actions (Dye = Potion)

Just copied Nanaki's

XHB 1 Most healing actions XHB 2 DMG actions

Valen Bree

WHM Level 100

Bars stacked with bar 1 on bottom and 4 on top

Bar 1 binds are generic, 2 uses [Ctrl]+, 3 uses [Shift]+, 4 uses [Alt]+

The layout I use for my WHM, will most likely change if I run into issues while attempting harder content.

All hotbar keybinds are arranged as follows
1: QERF
2: CV12
3: 345T

A controller layout for comfort and efficiency

View a full explanation for this layout:

https://youtu.be/Ga2kzBKgDcw

Single-target heals on left, damage and damage buffs on right, buffs in center, and AOE heals on double-right

SHING SHING SHING

Damn, this is a lot of buttons.

Finally

'Twas I who fought the dragon

Boom boom bakudan

Splorp splorp splorp, pretty picture!!

Mysharona

Like paladin but edgier

The VerHotbar

Basic skills on right, AOE on left, buffs on cross.

Something something Hokage, Believe it!