What I've found to believe in Nighthold is that each type of spec has a chance to shine in this raid.
If your spec is great at bursting down priority adds--there is a boss encounter for you.
If your spec is great at sustainable single target damage--there is a boss encounter for you.
If your spec is great at AoE damaging low health mobs--there is a boss encounter for you.
If your spec is great at spread-out council fights--there is a boss encounter for you.
Not all specs are going to shine on each and every NH boss encounter. Some players may rock the top of the dps charts in your guild but that could be that they are an exceptional player compared to the rest of your group. Does this mean that all specs are equal and balanced? No. But it also doesn't mean that Affliction is going to succeed in each and every fight in NH. Sometimes it's best for your raid team to let certain teams tunnel on fights because the comparative advantage of them dpsing adds isn't as high as just tunneling the boss.