This might just be me and my habits carrying over from XI, but it's always good to have abilities available if you need them. Right now, I'm at 30 with CNJ (doing WHM quest, just so I don't have to do it later if I choose to level it further). I also think it's a good idea to push MRD for those abilities as well.
I think it's a good idea to have Stoneskin.
FFXIV: Fat Chocobro (Balmung) Level 50 WHM, SCH, BLM, PLD -- MIN, GSM,
FFXIV: Fat Chocobro (Siren) MNK: 21