Maybe I don't get it, or didn't see the exact point in the 'No fucs-manifesto-thread' why it should be faster (so, feel free to point me there ;) ), but...

...honestly I simply don't know if a 'target-target' or 'focus-target' is realy quicker, when changing targets (and by targets I mean the target of your 'main', so the target you want to dps), because I would guess, since both 'focus' and 'target' are known to the client, that what WoW would do for a :

/cast [target=focus-target] ...

is to evaluate on the client the ID (or name, or whatever) of the thing stored in 'focus' and send something like '/cast [target=ID-target] ...' to the server and this would be the same for '/cast [target=target-target] ..' , so I honestly don't see why 'target-target' should be faster for casting the dps-spell ...

..what might be the case is, that setting the 'target' might be quicker than setting the focus, but in both setups this would only happen when the leader has to change (so in your suggested setup, when he dies), and this shouldn't be every second...

What I would see as a 'con' against the 'target-target' option is, that when you PVP you might have some problems:

1. You point your enemy directly to your main-toon (because all your slaves have him as their target)
2. You have a fixed order of 'mains' (if you use the exact macros from the 'no focus...')
3. You would have problems navigating your group when they are split and to far away for follow (happens often in AV with the graveyards) (this is also true for most fous-setups)
4. You can't use '/castsequences' with 'reset=target' in your macros (because your target will allways be the 'main')

Honestly, some of this limitations are also true for using 'focus' (..and thats why I use a customized FTL for this...).