So, the way the fight went, Duchess opened, and then Nekhret used his A2 against Cardinal. The Stoneskin shield got brought down to about 5% remaining. Then, Nekhret used his A3 on Duchess, and magically the Stoneskin shield on Cardinal was returned back to 100%?
Same thing happened to me this morning. UDK w/ Stoneskin, saw the shield bar drop to around 10% after my nuker hit him and jump back up to full on the next hit.
Luckily he was a 1-man defense team so I was able to burn him down on the next round.