I'm not sure how important this spell is, in combat log, I do a lot more hitting than mobs do, so things that trigger from MY hits are more important than things that trigger when mobs hit me. However, it's a change. Maybe it was always this way, and the examine window has been updated, or maybe it's part of an effort to reduce lag. I'd have to guess. But if you compare Shroud of Bertoxulous 8 vs 9 you'll see a sentence "this effect can only trigger..." has been added. If mobs were hitting us 6 times per second, then I could see worrying about it. I hope they explain at some point why this change and whether it was always like this, and etc. It wasn't in the BoL announcement.