If you're a WHM like me who often casts Cure on a full-health person just to get cureskin up, you will heal for 0HP and not get any MP returned. Raetic costs can really hurt then.
This is something I would probably build a swap around based on the targets HP, especially if mana was an issue.
If you are cure-skin bombing though I am going to assume that you have some external sources squaring away your mana or you are meleeing with a yagrush.
Cure skin bombing is actually really efficient MP-wise with a Raetic +1 if you are using Cure 1 since it's already super cheap, and gets really powerful for how much it costs.
Cure 1 with 2 Raetic +1's still only costs 12 MP tops.
I keep Cure 1 cureskin on my tanks as much as possible. Even if I cure for zero it's only 12 MP. Which usually regens back up before the next cast. If I cure for at least 200 HP, it's literally free, zero MP.
Cure 1 with two raetic +1's heals for 410 HP, or 533 HP if you have a +30% Cure received PLD. That's translates into either a 200 HP Stonekin, or a 261 HP Stoneskin respectively assuming you have the Ambuscade cape and +2 Empyrean Body, for like no MP cost most of the time, or very little at most.
That's actually a lot of mitigation if you keep it up full time.
That's not even counting the +44% Conserve MP I have in my cure set, which would drop the average MP that I do spend on it even lower.