One thing i find REALLY annoying is the display of teammembers HP:
I.E when you get out of range and come back to your team they all show with their UNBUFFED hp. This is so g.d annoying and sometimes makes it hard to know who to heal in a group or even when to heal!!
Your whole team looks half dead if you get out of range and back.. until you target them that is.. VERY ANNOYING.

Same goes for damage. You cant really see whos taking damage before they are down to their BASE unbuffed hp.
This goes for PVP aswell. Your target is at full HP until you get it down to base HP..