This along with the UI and Queues are my deal breakers. Mainly queues because whats the point of complaining about things in-game when you cant even get in.
However, this is a completely game breaking bug. How is a healer for a raid or in pvp expected to click on their teammates character alone to select them. Sure you can see who has low health above their name and then try to find them in your raid frames (where they will have full health) but by the time you do that, they'll be dead. Because healing in this game requires such burst at times and like all games is purely reactive, when you take away THE MOST IMPORTANT TOOL IN A HEALERS ARSENAL and expect no one to care, you're going to piss a lot of people off, myself included.
This is a non-issue for dps/tanks, so if you're one of those keep your mouth shut, no one cares that yours is working properly. This is an issue that effects all RAID groups, regular flashpoint group sizes end up working for the most part (even if you have party frames = raid frames selected) and just because it works for you once in a while doesn't mean its's perfect and doesn't need fixing. Apart from the server issues, this is what all of the devs should be putting their effort towards fixing.