It would be pretty hard to take 3 crushings in a row on curator if you are shield blocking every time it's not on cooldown.
I took a quick look at one of my old wws from that fight and it looks like he hits on average around once every 2 seconds.
I got 6 crushes in the entire fight I looked at and it was on the occasion where he fit 3 attacks in between SB cooldowns. So 2 blocks, and then 1 crush never 3 in a row. Should be next to impossible unless you weren't shield blocking when it was up.
It's possible your healers just weren't paying attention because they are used to healing a tank who takes less damage per hit. You'd need the combat logs to know for sure.