As mentioned previously Fear does not affect Undead of any type. Also, a lot of dragonkin and some demons are immune (specifically the larger ones that you'd like to CC).
Also, the focus macro was touched on, but not explained in detail.
Type "/focus" on your CC target (or make another macro do it) and then a macro containing the following:
replacing "Banish" with the spell you need to cast.Code:#showtooltip Banish /stopcasting /cast [target=focus,harm,nodead][] Banish
As you've mentioned Earth Elemental, you can also use Stoneclaw totem (to stun persuing or loose mobs), and Earthbind Totem (with glyph) to aoe Root (with the same restrictions as Druid's Root).