using the focus method you can set it up simply using the following:

bind the followng macro to "f" and assign to both the mage and shaman

/target insertnameofpaladinhere
/follow
/focus



now on your mage bind the following to key "1"

/cast [target=focustarget] Fireball

now on your shaman bind the following to key "1"

/cast [target=focustarget] Lightning bolt

press "f" to make your followers start following your main.
run up to a mob, tap the back key to stop your followers following your paladin
continue up to the mob and target with the paladin

now whatever you target with your paladin, by pressing "1" your followers will cast their spells at that target (no more alt tabbing)

take a look at the macro codex in the macros forum, as there are lots more examples and methods of doing this