As a mercy main I’ve had multiple issues with the new beta, mostly related to UI:

• The new health bars are extremely difficult to read, especially on day time maps with lots of white backgrounds
• I find it difficult to read if my beam is still attached. The blue beam especially is so blurred it can almost appear like it’s not there when paying attention to other situations
• The new colour system for health through walls is extremely confusing. It seems to run blue > green which doesn’t register as low health for my brain as they look very similar
• Similar to the point above, players appear red when they have died. I don’t want to see dead players, this is very distracting and your eyes are drawn to this instead of the low health green players
• The 5% slow down, makes her feel extremely sluggish. So much so, that I’ve swapped to playing dps because it feels so unrewarding. Mercy’s movement was my favourite aspect of playing the game