I use a damage shield so its pretty simple to see.
What happens is this:
Fight starts, me and mob is taking turns as intended.
MOB decides to cast a nano (of course it shows up in my NCU about 1 s before casting animation even starts). When casting animation stops I get hit 2 times by the mob. But my damage shield only deals one damage for one of those hits. Its a consistent bug. If MOB heals, I get hit twice, if MOB use a dot, I get hit twice. If I get rooted, I get hit twice and so on.
Try to defend against Frost of Coronet and two crits...