IMO 5.4 Affliction is looking like great fun. New Soul Swap is pretty good design, and combined with AD gives the spec an insane amount of depth. I don't recall ever having to think so much about how to play optimally for any caster spec.
I don't see the problem with the current iteration at all... Affliction and Demo are very close, or seem to be from all sources I have seen including doing all PTR tests myself. Affliction is a bit better on sustained 2-3 target DPS, while Demo can burst more and has better AoE in almost all circumstances. Destruction is still strong on 3-4 fights. For the lowest overall spec that's not bad at all if you look at previous patches. So many pure classes have had 100% useless specs almost every patch.
There will always be a strongest and a weakest spec, no matter how hard you try to balance things, unless the specs are made so similar that they have almost no differences. If you are serious about providing the most you can for your raid, you will always be forced to the best spec for a fight. If you don't care that much about optimizing, why do you care so much about balance?