Was this part of 2.1? The only thing mentioned in the patch notes is damage will interrupt during pvp, I used to be able to just spam stoneskin when a healer died and survive a pull until they ran back now it gets interrupted constantly. I also used to spam it when I knew death sentence was coming on twin, now the only time I can get it off is if I get lucky or if I start casting when she turns to fireball and ds comes right after so I don't get hit during cast.