Well, since I was going to talk about some UI issues I thought could use improving, and most have been covered here. I'll just tag along and add me piece to it.
As a Healer, It's kinda a pain having to look in 3 different locations of the screen for the people/companions I need to heal.
I need to watch the action bar for my health, bottom left corner for my companion. Middle left for party members, tiny bar under party member health bar for their companion.
Raid frames are OK, but not customizable enough, and don't work at all if you have to worry about a party members companion.