There is one thing that I don't find I understand is the point to not using the focus. Stay with me now i understand that the point is to use focus for CC and the like but let me try to explain how i see targeting:

In wow as multiboxers we basically have two target "slots" per character. Focus target and current target each of which with proper macros can function exactly like the other:
/cast [target=focustarget]
/cast [target=targettarget]

Thus if you have these two slots that work about the same lets consider the subtle differences... the big one is that focus remains more constant and can only be cleared with /clearfocus or by setting a new focus, thus none of the problems with accidentally tab targeting or losing target cause of looting or skinning or anything else that may cause your current target to be lost.

Now as for CC when using focus to designate main. You still have your other target "slot" which in this case is current target.

So when using focus:
button1: /cast [target=focustarget, harm] pewpew spell
button2: /cast polymorph

the dps spell lands on your mains target and the polymorph lands on your current target which can be aquired through an assist button prior to combat or during combat. If you have multiple characters that can CC, the use of round robin on your assist button will allow you to set different CC targets.

The reason I find this to be the better solution is because the CC targets are less permanent than you main...Therefore you should use the more permanent target "slot" (focus) to designate your main and the more volatile target "slot" (current target) to designate CC.