I don't think I saw this advised so far so~

Make sure to pick a sect that's appropriate for both the fight and the party composition.

If you're in an 8-man and your co-healer is a SCH, you're best to be in Diurnal since Nocturnal and SCH Galvanizes overwrite and just cause an overall massive headache.

When with a WHM you can pick either Nocturnal or Diurnal depending on the fight. Generally speaking double HoTs ticking in a low HPS fight allows for higher time from both healers. Pick Nocturnal in the more HP intensive fight where mitigation would lead to less overall hassle and derps.

Finally, when with an AST, well, I guess whoever picks first wins, or ask if your co-healer has a preference =p I personally just default Nocturnal since most ASTs I've partied with tend to prefer Diurnal.

Cards in the current incarnation are "GO FOR BALANCE OR BUST" but having knowledge of how each class/job plays also allows you to pick an appropriate target for other cards you'll eventually draw and have to use. Everyone has their preferences (Arrow seems to be a huge point of contention overall ATM), but there are definitely certain choices that make more sense than others.