I don't know maybe I've been using FTL too long and just think the right way, but it seems to be just as simple as focus for me.

I just made a template macro for damage spells and one for healing. Now when I want to add a spell I just copy paste to a new macro switch out the name of the spell copy the same macro to all chars and I'm done. With JambaDev's FTL macro creator it's easier than ever. /click JambaFTLTarget or Assist and you're shooting things dead before you know it.

HKN has a template setup, as does ISBoxer, so really most people are able to be up and running with FTL and really not know what the heck is happening other than it works.

Is it necessary? Nope
Is it the easiest setup? Nope
Is it the easiest to use? I would say so

But if you PvP and don't have time to fuss with which button to press to change leaders, it's awesome.
If you want to have the ability to "pseudo-focus" 2 targets then it's the only way to go.
So really I guess it's up to the player to decide which they want...