Threat bars stand out because that's the point. Important things stand out when they have too. People who lost a lot of health stand out more then others too. And my Grid has threat, but it's not a healer specific UI. I tanked with it too. Grid shows who has aggro, threatmeter shows 3 people so I can easily use my hands on people who overaggro or come to close to the tank. Both when I'm tanking and healing. Grid shows all the debuffs I can cleanse, Beacon, etc. Quite frankly, it shows all te information I needed for both a tankadin and healadin as a non raidleader. I was the #1 healer in the guild, not because I or my guild was any good, but mainly because I saw just what I needed to see, and a lot of other people in my guild didn't.