Yup, Bardham is when Augmented Shire starts falling off. I believe Shisui is still ilvl270 but bardham is 273. By Castrum though, you shouldn't have any signs of Shire gear left. It's just a problem. (That I personally experienced due to my own derp.)
Besides what other people have said, there is a big difference. I had to abuse CDs and really plan out my shieldings much further in advance then normal and often it would take at least 2 lustrates and an Adloquium to bring the tank back from the brink. Compared to the 1 lustrate in my regular healer gear. No one should be in augmented shire by Castrum. Not even a DPS. I honestly am surprised they didn't boot me for the mistake, cause they had every reason to! It reminded me how forgiving and kind this game's community can be.