If I see a WHM partner, I'll decide Sects on a per battle basis. If incoming damage is spikey, I prefer Nocturnal to soften the initial impact with WHM patching up. For battles with more sustained, but predictable damage, I'll go Diurnal and focus maintaining HoT's. It's pretty flexible, and you're only really shoehorned into strictly Diurnal when paired with a SCH.