WoW is hands down the easiest game to box. I 5-box mixed teams where the DPS are casters in some and melee in others. It is even possible to have a mixture of the two.
There are probably five techniques that will be helpful to you (in order of importance):
1. Follow. This is the most important method for moving your team around outside of combat and in many situations in combat as well.
2. A way to break follow when you want your slaves to stay in a particular spot. This is a specific and very useful example of item 4 below. A quick tap on a formation key (see item 5 below) can also be used to do this.
3. Interact with Target (IWT) - see
WoW: Interact with Target and watch MiRai's video. This can be used in a range of ways: make your melee characters run up to a target and attack it, interact with quest givers/vendors, orient your characters towards their target.
4. Independent slave movement keys (Mapped Key Wizard, Straight Key Broadcast, Target = Window: All w/o Current) - these are helpful for moving/strafing caster slaves out of fire, etc. Many people have their normal (master) movement on WASD and use the arrow keys to move their slaves only. I use a variation of that on a G13. Note that your slaves will tend to get out of "sync" over long/movement heavy fights and you may need to bring them back together with IWT or Follow.
5. Formation keys (there are some examples created by the Quick Setup Wizard - you just need to give them a Hotkey) - other situations require you to spread your team to keep distance between them for example.