Bars are always extremely transparent, hard to see the health bars. #8
I noticed the same issue, but only when going in and out of the obelisks in Mythic 10+ for the awakened affix. I found that a /reload works to fix it, but it's somewhat inconvenient considering sometimes you have to pull the next mobs immediately after exiting the portal. It pretty much blinds you to whats going on while reloading as well.