Just thought I'd add my two cents. As Ganukay mentioned, it's relatively easy to cap cure potency without using a body piece, but there are more things to look at.
First, the difference between HP recovered by Cure IV and Cure V. As a Whm, you'd tend to use Cure V more because of the enmity properties, making it safer to spam (especially with refresh atmas).
Secondly, since you'd use Cure V or VI over IV, there's usually a larder degree of "overcuring".
Since it's been discovered that the Afflatus Solace enhancement increases the amount of damage absorbed by the Stoneskin, and the fact that the amount that Stoneskin will absorb is based on your cure when it lands (as opposed to HP recovered), you could actually think about it exceeding the cure potency cap.
The +1 version converts an extra 5% of your cure into stoneskin, and the +2 converts an extra 10% into stoneskin. If you're going to end up overcuring anyway, it's a nice bonus to damage mitigation.
Not really a disappointment.
Noble's is only the better choice now if you can't reach the 50% cure potency cap in some other way. Here's the set I'm working on:
There's 40%. With atma of the rescuer in abyssea, you have 50%. If you don't have that atma or aren't in abyssea, Medicine Ring is also an option for that extra 10%
So with some mathematics I figure (in abyssea) my Cure V PLUS my cureskin brings the total to 1258 (28% cure potency) with this for body and 1296 (38% cure potency) with Noble's Tunic.
Now, in practice on Koghatu I noticed the extra tiny bit of cureskin to help mitigate damage (and help the taru monk stay alive) better than the Noble's did.
My personal preference is to macro this piece in for single target Cures and to use Noble's (or whatever cure potency I may get) for my Curagas.